Great diagnostics, but... Rated 3 out of 5 stars

After I updated to the latest Flash player and upgraded to Firefox 3.6, the Tamper Data (11.0.1) add-on caused issues with Firefox: I cannot open a new browser window. Ctrl-N, javascript window.open() and right-click "open in new window" are all broken.
This cleared up after I disabled the Tamper Data add-on. Perhaps some weird incompatibility with the notoriously buggy Adobe Flash player? Uninstalling Flash did however not clear up this issue.