Freezing up--Plist files?

Hi.

I'm running Final Cut Pro 7.0.3, and while working on a project (that had been running fine), I started running into some odd stuttering problems that were a little annoying. So, as always when something weird is going on with FCP, I deleted the Plist files in preferences. Reopening FCP now takes an extraordinarily long time and every time I hit play I get the rainbow loading ball for about 10 seconds before it plays.

Looking into my preferences file now, there are no finalcutpro.plist files anymore--usually they are regenerated when I reopen FCP.

Any ideas? I've got a video project due in the next couple of days and as it stands I can't work at all on it, so any help ASAP would be very appreciated!

--Another detail: it started acting up when I started editing footage that's HD as opposed to the standard def stuff I was working with. However, the stuttering effect (and now the complete breakdown) is on all footage, not just the HD stuff.