Stalled Timeline

Hi all:
I have one project open and the timeline keeps stalling with the spinning ball. Sometimes it takes over a minunte to disappear, but it comes back again. Many moons ago I had this problem and I can't remember your advice as to resolving this issue, although whatever it was, it worked. Sorry to be asking again. Was it emptying the cache? If so, I can't remember how to do that.

OS X 10.6.8
FCP 7
MacPro 2.66 GHz Dual Core Intel Xeon
8 GB RAMM

All of the harddrives have at least 40% empty space and I have run both Disk Warrior on all of them successfully and I zapped the p-ram too. Still stalls. Any advice would be greatly appreciated.
Thank you,
Stan

Please ignore this request. I found the earlier email and am taking care of the problem. Thank you.