We have recently migrated all of our workstations to a different Windows domain at our office. Some folks were getting the following error when trying to open a DataSet in Visual Studio 2005:
Key not valid for use in specified state
The problem can be caused by the change of a username from the old domain to the new domain. Visual Studio is not able to properly decrypt some its settings.
The fix is to rename/delete the following file:
C:\Documents and Settings\YOUR USERNAME\Application Data\Microsoft\VisualStudio\8.0\ServerExplorer\DefaultView.SEView
You will now have to add back all your databases to the Server Explorer toolbox (but you only have to add them at a later time as you need them).
Thanks to Robert Stam for this tip.