FYI, the way to stop that compatability check is to type into the URL box this...
about:config

and then right click anywhere in the browser window and select...
New: Boolean

And enter this as the name:
extensions.checkCompatibility.7.0

and select False for the value

(note that the extensions.checkCompatibility.7.0 has to be changed every time it updates, so if you are on version 6 you would use extensions.checkCompatibility.6.0)