The last weeks I done a lot of test because of the memory leaks using .innerHTML or events (closures). When building some test pages I ran into a problem. I reached 65.000 handles for iexplore.exe. From time to time I got a dialog box asking if I want to send data to a different location (the same question you get if you post data to a different domain). I clicked on yes, I clicked on no - both buttons are working, and my AJAX method, too. But some requests later I got the dialog box again, ...and again.
If you have a look at http://www.start.com/  or http://www.live.com/  you will see that the memory and the number of handles used in iexplore.exe is increasing on a lot of features you use, like minimizing or moving controls, adding new gadgets,...
If you press F5 (reload) the handle count will not decrease to an initial value. Another test showed me that an empty HTML page can increase the number of handles used on every page refresh, it was about 2 handles per page. This means that you can only open this page about 32.500 times. ;)
I will put an demo web page online during the next days.