I just recently upgraded my wordpress instance to 2.2. Late last week I noticed that in Firefox (and camino on my mac) the blog looked fine on the front page. However in IE and Safari, only one (old) post showed up and the sidebar didn’t load at all.
I was about to blow away WordPress all together and build it up from scratch but before doing that I disabled ALL my plug-ins. Wa lah! everything was back to normal. I re-enabled my plug-ins one at a time and discovered that TwitThis 1.1 was causing the problem. I’m not sure if it was TwitThis, or WordPress 2.2, but everything is back to normal!