Originally Posted by Prospero

This is an update which hopefully might help others.

Running CCleaner helped but after a few days FT would slow down again, so it was a case of rinse and repeat.

i was experiencing other performance issues with my iMac, particularly Finder which behaved sluggishly. This led me to think my Mac OS X system wasn’t quite right - while the hardware was new, the system had migrated over from an older iMac. So I scrubbed the hard drive and ran a clean install of Mac OS.

What a difference. The system, Firefox, FT have been firing on all cylinders since.