I cleaned out all the caches, cookies, saved sessions, etc., in FF before the running Disk Utility. I haven't zapped the PRAM yet - thanks for the reminder about that. If it still acts up, that'll be next on the list.
So far, it seems happy. About 480 MB of RAM used by FF for 6 tabs, but it usually takes a day or more for it to go nuts...
Thanks.
Cheers,
Scott.