I have this problem and it happens once in a while. I have only seen this in IE7 on Windows Vista when I start Google Reader.
iexplorer.exe is still running as a process in the background and has to be killed manually or there will be problems to run IE7 again.
Have anyone else run into this problem?
Since installing IE8 Beta 2 I have not had this problem though. On the other hand I initially had problems with YouTube in IE8. After cleaning up among the installations, reinstalling some and uninstall some plugins I had installed for IE I got YouTube to work fine in IE8. Did not have time to isolate the problem though. This problem did also result in having iexplorer.exe running after the crash.