diff --git a/CloverApp/Clover.xcodeproj/project.pbxproj b/CloverApp/Clover.xcodeproj/project.pbxproj
index 9008c795a..1fe11893e 100644
--- a/CloverApp/Clover.xcodeproj/project.pbxproj
+++ b/CloverApp/Clover.xcodeproj/project.pbxproj
@@ -1309,7 +1309,7 @@
 				CODE_SIGN_IDENTITY = "-";
 				CODE_SIGN_STYLE = Automatic;
 				COMBINE_HIDPI_IMAGES = YES;
-				CURRENT_PROJECT_VERSION = 1.22;
+				CURRENT_PROJECT_VERSION = 1.23;
 				FRAMEWORK_SEARCH_PATHS = (
 					"$(inherited)",
 					"$(PROJECT_DIR)/Clover/Frameworks",
@@ -1336,7 +1336,7 @@
 					"$(PROJECT_DIR)/Clover/Library",
 					"$(PROJECT_DIR)",
 				);
-				MARKETING_VERSION = 1.22;
+				MARKETING_VERSION = 1.23;
 				OTHER_LDFLAGS = "";
 				PRODUCT_BUNDLE_IDENTIFIER = org.slice.Clover;
 				PRODUCT_NAME = "$(TARGET_NAME)";
@@ -1357,7 +1357,7 @@
 				CODE_SIGN_IDENTITY = "-";
 				CODE_SIGN_STYLE = Automatic;
 				COMBINE_HIDPI_IMAGES = YES;
-				CURRENT_PROJECT_VERSION = 1.22;
+				CURRENT_PROJECT_VERSION = 1.23;
 				FRAMEWORK_SEARCH_PATHS = (
 					"$(inherited)",
 					"$(PROJECT_DIR)/Clover/Frameworks",
@@ -1383,7 +1383,7 @@
 					"$(PROJECT_DIR)/Clover/Library",
 					"$(PROJECT_DIR)",
 				);
-				MARKETING_VERSION = 1.22;
+				MARKETING_VERSION = 1.23;
 				OTHER_LDFLAGS = "";
 				PRODUCT_BUNDLE_IDENTIFIER = org.slice.Clover;
 				PRODUCT_NAME = "$(TARGET_NAME)";
diff --git a/CloverApp/Clover/ThemeManager/ThemeManager.swift b/CloverApp/Clover/ThemeManager/ThemeManager.swift
index a2e3fc1af..b9780f447 100644
--- a/CloverApp/Clover/ThemeManager/ThemeManager.swift
+++ b/CloverApp/Clover/ThemeManager/ThemeManager.swift
@@ -557,8 +557,10 @@ final class ThemeManager: NSObject, URLSessionDataDelegate {
     }
     return false
   }
+  
   /// Return the path for a given theme, if the download succeded
   public func download(theme: String, down: ThemeDownload, completion: @escaping (String?) -> ()) {
+    let advice = "Try to refresh the list by pressing the Refresh button below."
     self.statusError = nil
     if let sha = self.getSha() {
       let shaPath : String = self.basePath.addPath(sha)
@@ -573,13 +575,21 @@ final class ThemeManager: NSObject, URLSessionDataDelegate {
             try fm.createDirectory(atPath: themeDest,
                                    withIntermediateDirectories: true,
                                    attributes: nil)
-          } catch {}
+          } catch {
+            let desc = "Unexpected error: '\(error)'"
+            let e = NSError(domain: "org.slice.Clover.Download.Error",
+                            code: 3000,
+                            userInfo :[NSLocalizedDescriptionKey : desc])
+            
+            self.statusError = e
+            completion(nil)
+            return
+          }
         }
- 
+        
         let plistPath : String = "\(themeManagerIndexDir)/Themes/\(theme).plist"
         let themePlist = NSDictionary(contentsOfFile: plistPath)
         if let files : [String] = themePlist?.allKeys as? [String] {
-          // ---------------------------------------
           let fc : Int = files.count
           if fc > 0 {
             var succeded : Bool = true
@@ -617,17 +627,43 @@ final class ThemeManager: NSObject, URLSessionDataDelegate {
               if succeded {
                 completion(themeDest)
               } else {
-               completion(nil)
+                if self.statusError == nil { // downloadFile() generate a specific error
+                  let desc = "Unknown error downloading '\(theme)' theme."
+                  let e = NSError(domain: "org.slice.Clover.Download.Error",
+                                  code: 3001,
+                                  userInfo :[NSLocalizedDescriptionKey : desc])
+                  
+                  self.statusError = e
+                }
+                completion(nil)
               }
             })
           } else {
+            let desc = "'\(theme)' index file contains no file to download.\n\n\(advice)"
+            let e = NSError(domain: "org.slice.Clover.Download.Error",
+                            code: 3002,
+                            userInfo :[NSLocalizedDescriptionKey : desc])
+            
+            self.statusError = e
             completion(nil)
           }
         } else {
+          let desc = "Unable to load '\(theme)' index file (not found or unreadable).\n\n\(advice)"
+          let e = NSError(domain: "org.slice.Clover.Download.Error",
+                          code: 3003,
+                          userInfo :[NSLocalizedDescriptionKey : desc])
+          
+          self.statusError = e
           completion(nil)
         }
       }
     } else {
+      let desc = "sha1 directory not found.\n\n\(advice)"
+      let e = NSError(domain: "org.slice.Clover.Download.Error",
+                      code: 3004,
+                      userInfo :[NSLocalizedDescriptionKey : desc])
+      
+      self.statusError = e
       completion(nil)
     }
   }
diff --git a/CloverApp/Clover/ThemeManager/ThemeManagerVC.swift b/CloverApp/Clover/ThemeManager/ThemeManagerVC.swift
index 298f3acaf..51cc5e3ed 100644
--- a/CloverApp/Clover/ThemeManager/ThemeManagerVC.swift
+++ b/CloverApp/Clover/ThemeManager/ThemeManagerVC.swift
@@ -455,7 +455,6 @@ NSComboBoxDataSource {
 
     let sr = self.sidebar.selectedRow
     if sr >= 0 && sr < self.dataSource().count {
-      // ---------
       self.isBusy = true
       self.spinner.startAnimation(nil)
       self.optimizeButton.isEnabled = false
@@ -464,7 +463,7 @@ NSComboBoxDataSource {
       self.targetPop.isEnabled = false
       self.nameBox.isEnabled = false
       self.installedThemesCheckBox.isEnabled = false
-      // ---------
+    
       self.manager?.download(theme: theme,
                              down: .complete,
                              completion: { (path) in
@@ -476,7 +475,9 @@ NSComboBoxDataSource {
                                   alert.messageText = "Installation failed".locale
                                   alert.informativeText = self.manager!.statusError!.localizedDescription
                                   alert.addButton(withTitle: "OK")
-                                  alert.runModal()
+                                  
+                                  alert.beginSheetModal(for: self.view.window!, completionHandler: { (modalResponse) -> Void in
+                                  })
                                 }
                               } else {
                                 if let themePath = path {
@@ -498,17 +499,20 @@ NSComboBoxDataSource {
                                       alert.messageText = "Installation failed".locale
                                       alert.informativeText = "\(error.localizedDescription)"
                                       alert.addButton(withTitle: "OK")
-                                      alert.runModal()
+                                      alert.beginSheetModal(for: self.view.window!, completionHandler: { (modalResponse) -> Void in
+                                      })
                                     }
                                   }
                                 } else {
                                   NSSound(named: "Basso")?.play()
                                   DispatchQueue.main.async {
                                     let alert = NSAlert()
+                                    let advice = "Try to refresh the list by pressing the Refresh button below."
                                     alert.messageText = "Installation failed".locale
-                                    alert.informativeText = "Theme \"\(theme)\" not found."
+                                    alert.informativeText = "Theme \"\(theme)\" cannot be downloaded.\n\n\(advice)"
                                     alert.addButton(withTitle: "OK")
-                                    alert.runModal()
+                                    alert.beginSheetModal(for: self.view.window!, completionHandler: { (modalResponse) -> Void in
+                                    })
                                   }
                                 }
                               }