Actually it did not disable your Kaspersky virus software just only the extension that was installed on Firefox by Kaspersky program.

http://forum.kaspersky.com/index.php?showtopic=215472

Same thing happened to me. Talked to Kaspersky. Internet Security 2012 is available and is fully compatible with FF6. My beef is that FF did not tell me about all the disabled add-ons until after completing installation.

I had that same issue with FF5 & contacted Kaspersky & they sent me the 2012 download before it went public.. They even fixed the FF/Kaspersky digital keyboard & URL Advisor issues too.. Thank You Kaspersky they were right on it  !!!

Thanks for all the responses! My beef, too, is that Firefox didn't alert me about this conflict until after the update installation was done. Nana41, thanks! I just now contacted Kaspersky, not as easy as it should be, & await their response.