Was having problems with restarting (wouldn't log off), closing windows,
closing the browser, getting pages to load.  Read posts about add-ons, and
tried disabling add-ons and then enabling them one by one and trying all the
problem functions after each change.  Was time consuming, but discovered that
disabling all things Google (was using Google Toolbar) worked.  I was using
Task Manager more than I've ever used it before, now seems to be back to
normal.  Thanks to all the relevant threads.