Why an immediate update Firefox 7 released just one day back? if some users accepted Firefox 7 update while add-on updates waiting to be installed, after updating to Firefox 7 those add-ons will be hidden or not visible in Add-ons manager (don’t worry they were not uninstalled for sure), as a temporary workaround Mozilla released Add-on Recovery Tool for Firefox 7 which recovers hidden add-ons,  Mozilla will soon release Firefox 7.0.1 update to fix this issue.

Here is the bug details.

Update : Firefox 7.0.1 update now available, check about window from Help menu.