This issue happened a few months ago and it was fixed at that time. It appears to be back.
If I leave the IE add-on enabled, Internet Explorer will hang on closing, either itself or in closing a tab. I'm also seeing "connecting..." in the tab. If I go to Task Manager and am fortunate enough to pick the right PID to kill, if I have attempted to close IE with multiple other tabs, I'll get asked the question about closing all tabs or just the current tab.
My testing with the Intrusion Prevention add-on disabled has so far not had any problems.
I'm not running the latest AV. I have SystemWorks Premier 2009 with AV 16.8.0.41, so, like last time, it wasn't a product update but a Intrusion Prevention Signatures update that likely caused the issue.