We have encountered a potential issue when your list of cached libraries on a specific machine/user account gets out of sync with the list of deployed libraries in a repository.
To workaround this issue we have found that you can clear you local list of cached libraries.
You need to go to the following location and delete the content (ensuring the Designer is not running) :
In XP:
C:\Documents and Settings\[username]\Local Settings\Application Data\Metastorm\BPM\Designer\LibraryCache
In Vista / Server2008:
C:\Documents and Settings\[username]\Application Data\Metastorm\BPM\Designer\LibraryCache
To get there you need to do more that Show Hidden Folders, you need to UNCHECK Hide protected operating system files as well.