Hello Hlynur here at the same company as gulag above,
we coult not reproduce the same error at this link above.

i tryed to uppgrade to version 5.0 we are using version 4.0 and i got an error i thing we need a new licence key.

Error :System.Web.HttpException: ? ---> System.IO.FileLoadException: ? File name: "CuteEditor" at System.Reflection.RuntimeFieldInfo.InternalGetFieldType() at System.Reflection.RuntimeFieldInfo.get_FieldType() at System.Web.UI.Util.GetNonPrivateFieldType(Type classType, String fieldName) at System.Web.Compilation.TemplateControlCompiler.BuildFieldDeclaration(ControlBuilder builder, Boolean fGeneratedID) at System.Web.Compilation.TemplateControlCompiler.BuildSourceDataTreeFromBuilder(ControlBuilder builder, Boolean fInTemplate, PropertySetterEntry pse) at System.Web.Compilation.TemplateControlCompiler.BuildSourceDataTreeFromBuilder(ControlBuilder builder, Boolean fInTemplate, PropertySetterEntry pse) at System.Web.Compilation.TemplateControlCompiler.BuildMiscClassMembers() at System.Web.Compilation.PageCompiler.BuildMiscClassMembers() at System.Web.Compilation.BaseCompiler.BuildSourceDataTree() at System.Web.Compilation.BaseCompiler.GetCompiledType() at System.Web.UI.PageParser.CompileIntoType() at System.Web.UI.TemplateParser.GetParserCacheItemThroughCompilation() === Pre-bind state information === LOG: DisplayName = CuteEditor, Version=4.0.0.5, Culture=neutral, PublicKeyToken=3858aa6802b1223a (Fully-specified) LOG: Appbase = file:///xxx/xxx LOG: Initial PrivatePath = bin Calling assembly : VinnuKerfi, Version=4.0.2124.33634, Culture=neutral, PublicKeyToken=null. === LOG: Publisher policy file is not found. LOG: No redirect found in host configuration file (C:\WINDOWS\Microsoft.NET\Framework\v1.1.4322\aspnet.config). LOG: Using machine configuration file from C:\WINDOWS\Microsoft.NET\Framework\v1.1.4322\config\machine.config. LOG: Post-policy reference: CuteEditor, Version=4.0.0.5, Culture=neutral, PublicKeyToken=3858aa6802b1223a LOG: Attempting download of new URL file:///C:/WINDOWS/Microsoft.NET/Framework/v1.1.4322/Temporary ASP.NET Files/vinnukerfi/96701ce6/34d68d82/CuteEditor.DLL. LOG: Attempting download of new URL file:///C:/WINDOWS/Microsoft.NET/Framework/v1.1.4322/Temporary ASP.NET Files/vinnukerfi/96701ce6/34d68d82/CuteEditor/CuteEditor.DLL. LOG: Attempting download of new URL file:///C:/xxxx/bin/CuteEditor.DLL. WRN: Comparing the assembly name resulted in the mismatch: Major Version --- End of inner exception stack trace --- at System.Web.UI.TemplateParser.GetParserCacheItemInternal(Boolean fCreateIfNotFound) at System.Web.UI.TemplateParser.GetParserCacheItemWithNewConfigPath() at System.Web.UI.TemplateParser.GetParserCacheItem() at System.Web.UI.TemplateControlParser.CompileAndGetParserCacheItem(String virtualPath, String inputFile, HttpContext context) at System.Web.UI.TemplateControlParser.GetCompiledInstance(String virtualPath, String inputFile, HttpContext context) at System.Web.UI.PageParser.GetCompiledPageInstanceInternal(String virtualPath, String inputFile, HttpContext context) at System.Web.UI.PageHandlerFactory.GetHandler(HttpContext context, String requestType, String url, String path) at System.Web.HttpApplication.MapHttpHandler(HttpContext context, String requestType, String path, String pathTranslated, Boolean useAppConfig) at System.Web.MapHandlerExecutionStep.System.Web.HttpApplication+IExecutionStep.Execute() at System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously)