Adding to my comment a few posts above: I mentioned having no cookies issues, but that seemed to only apply to my wired connection. When I tried a couple of computers connected to the wireless, they did indeed have trouble negotiating cookies. I tried the temporary fix of checking the box at Security -> Web Filters -> Cookies
. Everything is working well now as far as I can tell.
Additionally I have reported the issue to Cisco's customer service department. As others have noted, they simply refuse to provide a previous version of the firmware. They actually went as far as to authorize replacement of the router, which I consider a pretty silly and costly solution to their problem. I have decided to just wait until the next firmware upgrade is issued. (Although my X2000 is one that does not have a power switch, and I'd really like to have one with a power switch. I've seriously considered swapping it for their replacement just to get that!