I'm so sorry I haven't gotten back top you on this. I saw your post just before I went to be on the 6th (well, really the early morning of the 7th) and then yesterday I had so many things to do that it completely slipped my mind.
But anyway, I checked the forum's error log and there isn't anything listed so far as any problems with PMs is concerned or even anything for you, so whatever is happening wouldn't seem to be a system error - it seems to be a browser error.
When you get the error, does the screen simply say just "runtime error" or is there more to it? If there is more, could you copy it down and post it here because honestly I'm not quite sure what's happening with your browser.