This would be an excellent addon for a multi-user environment - if it worked!
Unfortunately, when deployed globally the download here is not compatable with FF 3.5.3.
Although you can update from within FF Addons (which then makes it work) the restrictions you set do not affect other users. I guess this is because the other users have not (and cannot due to account restrictions) update the addon.
This is a big shame as it would very much simplify FF lock down for our school.
Please, is there anyone who knows a fix for this?