I've just discovered why gmail was having conniptions in Internet Explorer. I have started using coComments to track conversations (mostly on blogs) to which I have contributed a comment. I've been using the coComment extension for both Firefox and Internet Explorer.
There have been no problems in Firefox, but in IE every time I opened a message, it would automatically go back to my inbox after just a few seconds. Having just disabled the cocomment extension, my messages now stay open. Thankfully, I can just temporarily disable the extension when using Gmail in IE.
I've also added a coComment widget in the sidebar (for those who only read this in a feed reader - you'll have to visit the site to see it) which links to recent comments I've made. Starting to use coComment was the only thing I managed to do as part of the comment challenge.