We've been getting the same error with CS 5 and CS 5.5 on remote accounts on our Macs. Local accounts seem to work fine.
You might get some useful information if you examine the Catalyst log under:
/Users/[account]/Library/Application Support/Adobe/Flash Catalyst/workspace/.metadata/.log
In our case, the error came when the server was unable to lock a certain file (~/Library/Application Support/Adobe/Flash Catalyst/configuration/org.eclipse.osgi/.manager/.fileTableLock) on our server system.
As a fix, I'm going to attempt to move the file onto the local drive.
Don't know if you're having the same problems or not.
Hope this helps.