User-agent: Mozilla Thunderbird 1.0 (Windows/20041206)
Try this first:
1) Open the VE, get the error, close the VE, but leave Eclipse running
2) Do Project->Clean...->Clean ALL (all is very important).
3) Try the VE again. If you still get the error, please send us the
class in question so we can see if there is anything in there that could
cause this.