Q: My cooling fan won't stop kicking in on Mac Pro

Suddenly in the last week or so my cooling fan started kicking in while over the past 2+ years it has only run once or twice - now it won't stop!

I thought that it may have been due to an increase in RAM from 7G to 24G (3, 8G matched sticks) but after un-installing the 24G it was still running frequently, though not as much.

I have performed (in order) both a PRAM and SMC reset.  I have also repaired all discs, reset permissions and dumped render files (I primarily use my Mac for video editing in FCP X).

I am fearing now that this may in fact be due to recent updates to Lion (10.7.3) or FCP X (10.0.3)

In an attempt to get FCP X to run better (there are many bugs in the latest update as evidenced by numerous posts in that discussion area) I also contacted NVIDIA for updates to my graphics card and was told by them that it is not compatible with Lion.  I now have a Radeon card on order from the Apple store.

Any other advice??  This fan is not only an annoyance for me but as I also record voice-overs for my clients I simply cannot have it running all the time.