Aleksander,
Can you give a little more description as to when you see this problem? Is it on every page, and therefore you can't use your site, or do you get the operation aborted error only on login or logout, or after you've been logged-in, etc?
We tested quickly today with WinXP SP2 and we weren't able to see the operation aborted, but we weren't exactly sure how to test.
Also, if you try to perform the same action on this site or our demo site, do you have the same results (
sourcecoast.com/jfbconnect/demo)?
Thanks!