Hello sue. This sounds like some fishy Google move to get you in their services. Are you certain it's Firefox and not Google?

In any case, try checking Tools > Options > Applications and change the "mailto" service for "ask always" or something like that. Maybe that's your problem?

Hope this helps.

Thanks Morbus! Apparently it is a Google problem that coincidentally appeared after I downloaded Firefox. Google is working on a fix. Thanks for leading me in the right direction.

You're very welcome.