Add-ons Missing in Firefox 7

Mozilla has identified an odd issues were some desktop and mobile users have had some or all of their add-ons going missing from the add-ons manager after updating to Firefox 7. Don’t panic, your add-ons (and their associated data) are still there, just not showing up in the add-ons manager There will be an emergency Firefox update (7.0.1) in the coming days to correct this issue. In the meantime to get these add-ons to reappear install the Add-on Recovery Tool add-on and restart Firefox.

Source: Mozilla Add-ons Blog