XPCOM:EventReceiver

A few weeks ago FireFox automatically downloaded an update (1.5.05 I think) and I started having problems. My computer would keep running and running. When I closed all open windows and tried to do a restart I got an error message saying that Windows was closing program XPCOM:EventReceiver. That changed to an error window saying it was not responding and asked if I wanted to end task. When I chose that option it didn't stop - I just got another window asking me to end task. No matter how often I chose to end task it still kept running. I finally got it to close by clicking Start>Turn Off Computer>Restart several times.

I have googled XPCOM:EventReceiver and there is some indication that there is an incompatibility problem with FireFox and McAfee. The only McAfee program I am running is the FF search engine Site Advisor. This problem did not occur when I initially downloaded Site Advisor - just after the automatic FF update was installed. However the results of my google search were not really clear on what is actually causing the problem. Some said it was McAfee, others said it wasn't. Since then I have also downloaded the latest FF update (1.5.06). I am still having the same problem.

Has anyone encountered this problem before? Any ideas on how to fix it? Thanks.