diff --git a/src/Main/Base/Project/Src/Project/MSBuildBasedProject.cs b/src/Main/Base/Project/Src/Project/MSBuildBasedProject.cs
index 394a3b92c9..7d0a5aebd8 100644
--- a/src/Main/Base/Project/Src/Project/MSBuildBasedProject.cs
+++ b/src/Main/Base/Project/Src/Project/MSBuildBasedProject.cs
@@ -798,7 +798,19 @@ namespace ICSharpCode.SharpDevelop.Project
 				
 				InitializeMSBuildProject();
 				
-				project.Load(fileName);
+				try {
+					project.Load(fileName);
+				} catch (MSBuild.InvalidProjectFileException ex) {
+					LoggingService.Warn(ex);
+					if (ex.ErrorCode == "MSB4075") {
+						// "The project file must be opened in VS IDE and converted to latest version
+						// before it can be build by MSBuild."
+						Converter.PrjxToSolutionProject.ConvertVSNetProject(fileName);
+						project.Load(fileName);
+					} else {
+						throw;
+					}
+				}
 				this.ActiveConfiguration = GetEvaluatedProperty("Configuration") ?? this.ActiveConfiguration;
 				this.ActivePlatform = GetEvaluatedProperty("Platform") ?? this.ActivePlatform;
 				
diff --git a/src/Main/Base/Project/Src/Project/UnknownProject.cs b/src/Main/Base/Project/Src/Project/UnknownProject.cs
index 98979e0d9e..4686b9a514 100644
--- a/src/Main/Base/Project/Src/Project/UnknownProject.cs
+++ b/src/Main/Base/Project/Src/Project/UnknownProject.cs
@@ -6,22 +6,38 @@
 // </file>
 
 using System;
+using ICSharpCode.Core;
 
 namespace ICSharpCode.SharpDevelop.Project
 {
 	public class UnknownProject : AbstractProject
 	{
 		string warningText = "${res:ICSharpCode.SharpDevelop.Commands.ProjectBrowser.NoBackendForProjectType}";
+		bool warningDisplayedToUser;
 		
 		public string WarningText {
 			get { return warningText; }
 			set { warningText = value; }
 		}
 		
-		public UnknownProject(string fileName, string title, string warningText)
+		public bool WarningDisplayedToUser {
+			get { return warningDisplayedToUser; }
+			set { warningDisplayedToUser = value; }
+		}
+		
+		public void ShowWarningMessageBox()
+		{
+			warningDisplayedToUser = true;
+			MessageService.ShowError("Error loading " + this.FileName + ":\n" + warningText);
+		}
+		
+		public UnknownProject(string fileName, string title, string warningText, bool displayWarningToUser)
 			: this(fileName, title)
 		{
 			this.warningText = warningText;
+			if (displayWarningToUser) {
+				ShowWarningMessageBox();
+			}
 		}
 		
 		public UnknownProject(string fileName, string title)
diff --git a/src/Main/Base/Project/Src/Services/LanguageBinding/LanguageBindingService.cs b/src/Main/Base/Project/Src/Services/LanguageBinding/LanguageBindingService.cs
index 1104481b77..44279038ee 100644
--- a/src/Main/Base/Project/Src/Services/LanguageBinding/LanguageBindingService.cs
+++ b/src/Main/Base/Project/Src/Services/LanguageBinding/LanguageBindingService.cs
@@ -117,16 +117,13 @@ namespace ICSharpCode.SharpDevelop
 					try {
 						newProject = binding.LoadProject(provider, location, title);
 					} catch (XmlException ex) {
-						MessageService.ShowError("Error loading " + location + ":\n" + ex.Message);
-						newProject = new UnknownProject(location, title, ex.Message);
+						newProject = new UnknownProject(location, title, ex.Message, true);
 						newProject.TypeGuid = projectTypeGuid;
 					} catch (Microsoft.Build.BuildEngine.InvalidProjectFileException ex) {
-						MessageService.ShowError("Error loading " + location + ":\n" + ex.Message);
-						newProject = new UnknownProject(location, title, ex.Message);
+						newProject = new UnknownProject(location, title, ex.Message, true);
 						newProject.TypeGuid = projectTypeGuid;
 					} catch (UnauthorizedAccessException ex) {
-						MessageService.ShowError("Error loading " + location + ":\n" + ex.Message);
-						newProject = new UnknownProject(location, title, ex.Message);
+						newProject = new UnknownProject(location, title, ex.Message, true);
 						newProject.TypeGuid = projectTypeGuid;
 					}
 				} else {
diff --git a/src/Main/Base/Project/Src/Services/ProjectService/ProjectService.cs b/src/Main/Base/Project/Src/Services/ProjectService/ProjectService.cs
index b3b61115fc..542fb390b1 100644
--- a/src/Main/Base/Project/Src/Services/ProjectService/ProjectService.cs
+++ b/src/Main/Base/Project/Src/Services/ProjectService/ProjectService.cs
@@ -349,6 +349,12 @@ namespace ICSharpCode.SharpDevelop.Project
 			IProject project;
 			if (binding != null) {
 				project = LanguageBindingService.LoadProject(solution, fileName, solution.Name);
+				if (project is UnknownProject) {
+					if (((UnknownProject)project).WarningDisplayedToUser == false) {
+						((UnknownProject)project).ShowWarningMessageBox();
+					}
+					return;
+				}
 			} else {
 				MessageService.ShowError(StringParser.Parse("${res:ICSharpCode.SharpDevelop.Commands.OpenCombine.InvalidProjectOrCombine}", new string[,] {{"FileName", fileName}}));
 				return;