For quite some time I've had trouble with IE7 trying (and failing) to open links in emails & newsgroup messages.
Sometimes it'll even pop up when I click on email addresses instead of my email program.
Oddly, despite setting Firefox as my default browser, clicking on a link will still usually open up IE. I say usually because sometimes Firefox opens the link as instructed. Each time it comes up with this message in the address bar.
res://ieframe.dll/syntax.htm#
I've tried running regsvr32 urlmon.dll I think (it was some time ago) but it didn't fix the problem.
I'm running Windows XP home (with SP3) and have Firefox. I used to use Google Chrome and I think it was after I uninstalled Chrome that the problems began.
Tim