Slow Performance, Delayed Cursor, Spinning Ball

First of all, thank you all for such great advice on problem-solving over the years. It has been invaluable. I have a problem that recently popped up which I think might be an easy one to solve with your advice. Recently I have been getting the spinning color ball for 5 to 10 seconds before the function I designate. For example, if I drag a clip to the Viewer, I get the spinning ball before the clip appears. Also, sometimes when playing the timeline, the project stops and I have to hit the play bar for it to proceed. Also, sometimes the sync is out of whack and yet if I go back and play the same timeline a few minutes later, it is in sync. If I move the cursor from one point in the timeline to another, I get the spinning ball for 5 to 10 seconds. Any ideas?

OS X 10.6.8
FCP 7
MacPro Intel 2.66 Dual Core
8 GB Memory

Could be lots of things. The fact that it's just started out of the blue often points to drives that are getting too full. Do all your connected drives have more than 10% headroom?

Thanks, Jude. I'll check on that tomorrow and post comments on what I find.