Could your tell us what exactly you have set the AppleScript to do and what action is supposed to Trigger it please.
I have seen this using a modified Auto Response AppleScript that also changed my Status Message to Away.
I get the message if I play and change the Status message.
I have a second Script that changes the Status message back on ending a video chat and it is at this point I get the error message.
It seems that what I want to change it back to is saved but no longer matches what has been stored in the com.apple.ichatAgent.plist as the Status Message.
I hope this gives some clues.
10:56 PM Wednesday; April 1, 2009