Not sure if this is connected to our other more serious issue of Myriad crashing, but looking on the event log of the server, PSquared Twteeter generates an error eveytime it's used.  It still posts the tweet, but in the log is the following:

Faulting application name: PSquaredTweeter.exe, version: 2.0.1.0, time stamp: 0x52208803

Faulting module name: unknown, version: 0.0.0.0, time stamp: 0x00000000

Exception code: 0xc0000005

Neil