Gmail and Firefox 2.0.0.5 - issues with JavaScript?

Over the past couple of days I've noticed issues with the Inbox view of Gmail being extremely slow on Firefox (2.0.0.5, the current version).

Disabling JavaScript makes the load much faster (naturally), but even switching to Internet Explorer (7) works (with JS on).

With Firefox 2.0.0.5 already having a security issue, I wonder if updating was a good decision in this case. Perhaps 2.0.0.5 was released a bit too quickly?