I am getting this error when opening a DataSet designer (.xsd file):

Key not valid for use in specified state.

at Microsoft.VisualStudio.Data.DataProtection.DecryptString(String s) at Microsoft.VSDesigner.VSDesignerPackage.AppSettingsHelper.AddServerExplorerConnections(IServiceProvider serviceProvider, IList connections) at Microsoft.VSDesigner.VSDesignerPackage.GlobalConnectionService.Microsoft.VSDesigner.VSDesignerPackage.IGlobalConnectionService.GetConnections(IServiceProvider serviceProvider, Project project) at Microsoft.VSDesigner.DataSource.DesignConnection.GetConnectionFromAppSettings(String objectName, String propertyName) at Microsoft.VSDesigner.DataSource.DesignConnection.get_ConnectionStringObject() at Microsoft.VSDesigner.DataSource.DbSource.set_Connection(IDesignConnection value) at Microsoft.VSDesigner.DataSource.DesignDataSource.SetConnectionProperty(Source source) at Microsoft.VSDesigner.DataSource.DesignDataSource.ReadXmlSchema(DataSourceXmlTextReader xmlReader) at Microsoft.VSDesigner.DataSource.DesignDataSource.ReadXmlSchema(TextReader textReader) at Microsoft.VSDesigner.DataSource.Designer.DataSourceSerializationService.DeserializeToDataSource(String filePath, Object serializationData) at Microsoft.VSDesigner.DataSource.ProjectDataSourceDescriptor.LoadDataSource() at Microsoft.VSDesigner.DataSource.ProjectDataSourceDescriptor.Init(IServiceProvider provider, IVsHierarchy primaryHierarchy, UInt32 primaryItemId, Object primaryDocDataObject, UInt32 docCookie, IVsInvisibleEditor invisibleEditor, IDesignerHost host) at Microsoft.VSDesigner.DataSource.ProjectDataSourceStorage.EnsureInvisibleEditor(ProjectItem dsProjectItem, Boolean ensureWritable, Boolean createInvisibleEditor) at Microsoft.VSDesigner.DataSource.ProjectDataSourceStorage.GetDataSourceInternal(Object caller, ProjectItem dsProjectItem, Boolean ensureWritable, Boolean createInvisibleEditor) at Microsoft.VSDesigner.DataSource.Designer.DataSourceDesignerLoader.HandleLoad(IDesignerSerializationManager serializationManager) I have all my datasets in the same Project. The datasets reference a connection string in the app.config file. I have tried deleting this connection string and recreatingit but that did not help. Also, my account has just been migrated from non Active Directory domain to an Active Directory domain and my profile has been migrated as well. I suspect this may have caused the problem but I cannot find a solution. Everything else works except opening datasets. Any help would be appreciated.

I don't know if you'vegot an answer yet, but for my part the solution was the following:

Deletethe data connectionthe dataset is basedupon ("Data Connections" in Server Explorer),reconnect it and it should be working again.

The workarround was really funny

I just deleted the connection from Server Explorer, now when i reopen the datasets they work fine....

If any other solution please inform

Just had the same problem myself. Deleting and reestablishing the database connections worked perfectly. Thanks.