cannot add the specified assembly to the global assembly cache

I had this error when I tried deploy a WSP into a SharePoint farm, one of the DLLs needed to go into the GAC (global assembly cache.)  I checked the GAC and the file already existed, I tried to uninstall the file and got the error that the file was in use and could be deleted.  After doing some checking around I found the following link that resolved my issue:

__http://support.microsoft.com/kb/873195__

Basically you go into the registry and find go to the following locations:

·        HKEY_CURRENT_USER\Software\Microsoft\Installer\Assemblies\Global

·        HKEY_LOCAL_MACHINE\Software\Classes\Installer\Assemblies\Global

Find the entry for your problem assembly and remove it.  Then try and uninstall the assembly out of the GAC and redeploy your WSP.