ale said:Did you read and applied the entry 20090628 in /usr/ports/UPDATING?
If so, flash could be another source of sluggishness for ff, do you have it installed? What removing it from ~/.mozilla/plugins (npwrapper.libflashplayer.so)?
jnr said:Do you have any Firefox plugins installed? Try again with a fresh profile.
I noticed 3.5 pegging one of my CPU cores recently and fixed it by uninstalling a particular add-on.