diff --git a/src/Main/Base/Project/Dom/ClassBrowser/AssemblyTreeNode.cs b/src/Main/Base/Project/Dom/ClassBrowser/AssemblyTreeNode.cs
index b6f382bba4..ff499c969f 100644
--- a/src/Main/Base/Project/Dom/ClassBrowser/AssemblyTreeNode.cs
+++ b/src/Main/Base/Project/Dom/ClassBrowser/AssemblyTreeNode.cs
@@ -44,7 +44,11 @@ namespace ICSharpCode.SharpDevelop.Dom.ClassBrowser
 		
 		public override object Icon {
 			get {
-				return SD.ResourceService.GetImageSource("Icons.16x16.Assembly");
+				if (model.Context.IsValid) {
+					return SD.ResourceService.GetImageSource("Icons.16x16.Assembly");
+				} else {
+					return SD.ResourceService.GetImageSource("Icons.16x16.AssemblyError");
+				}
 			}
 		}
 		
diff --git a/src/Main/Base/Project/Dom/IEntityModelContext.cs b/src/Main/Base/Project/Dom/IEntityModelContext.cs
index 69295ef7b3..542c87d107 100644
--- a/src/Main/Base/Project/Dom/IEntityModelContext.cs
+++ b/src/Main/Base/Project/Dom/IEntityModelContext.cs
@@ -44,6 +44,11 @@ namespace ICSharpCode.SharpDevelop.Dom
 		/// Full path and file name of the assembly. Output assembly for projects.
 		/// </summary>
 		string Location { get; }
+		
+		/// <summary>
+		/// Returns whether this is a valid context (based on a existing and readable definition).
+		/// </summary>
+		bool IsValid { get; }
 	}
 	
 	public class ProjectEntityModelContext : IEntityModelContext
@@ -80,6 +85,10 @@ namespace ICSharpCode.SharpDevelop.Dom
 		{
 			return EntityModelContextUtils.IsBetterPart(part1, part2, primaryCodeFileExtension);
 		}
+		
+		public bool IsValid {
+			get { return true; }
+		}
 	}
 	
 	public class AssemblyEntityModelContext : IEntityModelContext
@@ -119,6 +128,10 @@ namespace ICSharpCode.SharpDevelop.Dom
 		public IProject Project {
 			get { return null; }
 		}
+		
+		public bool IsValid {
+			get { return true; }
+		}
 	}
 	
 	public static class EntityModelContextUtils
diff --git a/src/Main/SharpDevelop/Dom/ClassBrowser/ClassBrowserPad.cs b/src/Main/SharpDevelop/Dom/ClassBrowser/ClassBrowserPad.cs
index da5865ec00..891508f62b 100644
--- a/src/Main/SharpDevelop/Dom/ClassBrowser/ClassBrowserPad.cs
+++ b/src/Main/SharpDevelop/Dom/ClassBrowser/ClassBrowserPad.cs
@@ -2,13 +2,16 @@
 // This code is distributed under the GNU LGPL (for details please see \doc\license.txt)
 
 using System;
+using System.IO;
 using System.Linq;
 using System.Collections.Generic;
 using System.Diagnostics;
 using System.Windows.Controls;
+using ICSharpCode.Core;
 using ICSharpCode.Core.Presentation;
 using ICSharpCode.NRefactory;
 using ICSharpCode.NRefactory.TypeSystem;
+using ICSharpCode.SharpDevelop.Dom;
 using ICSharpCode.TreeView;
 using ICSharpCode.SharpDevelop.Project;
 using ICSharpCode.SharpDevelop.Workbench;
@@ -27,6 +30,50 @@ namespace ICSharpCode.SharpDevelop.Dom.ClassBrowser
 		public bool IsActive { get; set; }
 	}
 	
+	class UnresolvedAssemblyEntityModelContext : IEntityModelContext
+	{
+		string assemblyName;
+		string location;
+		
+		public UnresolvedAssemblyEntityModelContext(string assemblyName, string location)
+		{
+			this.assemblyName = assemblyName;
+			this.location = location;
+		}
+		
+		public ICompilation GetCompilation()
+		{
+			return null;
+		}
+		
+		public bool IsBetterPart(IUnresolvedTypeDefinition part1, IUnresolvedTypeDefinition part2)
+		{
+			return false;
+		}
+		
+		public IProject Project {
+			get {
+				return null;
+			}
+		}
+		
+		public string AssemblyName {
+			get {
+				return assemblyName;
+			}
+		}
+		
+		public string Location {
+			get {
+				return location;
+			}
+		}
+		
+		public bool IsValid {
+			get { return false; }
+		}
+	}
+	
 	class ClassBrowserPad : AbstractPadContent, IClassBrowser
 	{
 		#region IClassBrowser implementation
@@ -171,19 +218,33 @@ namespace ICSharpCode.SharpDevelop.Dom.ClassBrowser
 		
 		public static IAssemblyModel CreateAssemblyModelFromFile(string fileName)
 		{
-			var loader = new CecilLoader();
-			loader.IncludeInternalMembers = true;
-			loader.LazyLoad = true;
-			var assembly = loader.LoadAssemblyFile(fileName);
-			
-			IEntityModelContext context = new AssemblyEntityModelContext(assembly);
-			IAssemblyModel model = SD.GetRequiredService<IModelFactory>().CreateAssemblyModel(context);
+			try {
+				var loader = new CecilLoader();
+				loader.IncludeInternalMembers = true;
+				loader.LazyLoad = true;
+				var assembly = loader.LoadAssemblyFile(fileName);
+				
+				IEntityModelContext context = new AssemblyEntityModelContext(assembly);
+				IAssemblyModel model = SD.GetRequiredService<IModelFactory>().CreateAssemblyModel(context);
+				if (model is IUpdateableAssemblyModel) {
+					((IUpdateableAssemblyModel)model).Update(EmptyList<IUnresolvedTypeDefinition>.Instance, assembly.TopLevelTypeDefinitions.ToList());
+					((IUpdateableAssemblyModel) model).AssemblyName = assembly.AssemblyName;
+				}
+				return model;
+			} catch (BadImageFormatException ex) {
+				SD.MessageService.ShowWarningFormatted("{0} is not a valid .NET assembly.", Path.GetFileName(fileName));
+			} catch (FileNotFoundException ex) {
+				SD.MessageService.ShowWarningFormatted("{0} is not accessible or doesn't exist anymore.", fileName);
+			}
 			
-			if (model is IUpdateableAssemblyModel) {
-				((IUpdateableAssemblyModel)model).Update(EmptyList<IUnresolvedTypeDefinition>.Instance, assembly.TopLevelTypeDefinitions.ToList());
-				((IUpdateableAssemblyModel) model).AssemblyName = assembly.AssemblyName;
+			// AssemblyModel for unresolved file references
+			IEntityModelContext unresolvedContext = new UnresolvedAssemblyEntityModelContext(Path.GetFileName(fileName), fileName);
+			IAssemblyModel unresolvedModel = SD.GetRequiredService<IModelFactory>().CreateAssemblyModel(unresolvedContext);
+			if (unresolvedModel is IUpdateableAssemblyModel) {
+				((IUpdateableAssemblyModel) unresolvedModel).AssemblyName = unresolvedContext.AssemblyName;
 			}
-			return model;
+			
+			return unresolvedModel;
 		}
 		
 		void AppendAssemblyFileToList(string assemblyFile)
diff --git a/src/Main/SharpDevelop/Dom/ClassBrowser/Commands.cs b/src/Main/SharpDevelop/Dom/ClassBrowser/Commands.cs
index 17ce0e73f1..3287d4e4f9 100644
--- a/src/Main/SharpDevelop/Dom/ClassBrowser/Commands.cs
+++ b/src/Main/SharpDevelop/Dom/ClassBrowser/Commands.cs
@@ -23,11 +23,7 @@ namespace ICSharpCode.SharpDevelop.Dom.ClassBrowser
 				openFileDialog.CheckPathExists = true;
 				if (openFileDialog.ShowDialog() ?? false)
 				{
-					try {
 					classBrowser.AssemblyList.Assemblies.Add(ClassBrowserPad.CreateAssemblyModelFromFile(openFileDialog.FileName));
-					} catch (BadImageFormatException ex) {
-						SD.MessageService.ShowWarningFormatted("{0} is not a valid .NET assembly.", Path.GetFileName(openFileDialog.FileName));
-					}
 				}
 			}
 		}