Thanks Robert - my gut says it might be a little more serious than I originally expected. I couldn't work out how to take a snapshot or report of the corrupted files Disk Warrior couldn't fix - they may have indicated something to mac guru's on here.
It's ok at the moment (touch MDF) and I'm happily editing away, but I just know to expect a total crash at any moment. I'll be leaving everything on for the next few days (FCP, the drives, the lot) not to rock this boat.

Cheers.

Not sure if this is relevant but I have found these error files on my internal HD (via disk warrior) - I've attached a snapshot of the report:

I know that the bottom file (version p.list) was stored under library/prefs/final cut pro user data/FCP rescue 5 - might it be this program conflicting with FCP and causing crashes? Anyone experienced conflicts with this program?

I've posted this on a mac 'genius' board to see if I can fix anything before inevitably taking the machine in.

".plist" files are preference files and can sometimes become corrupted beyond repair. This is one reason why I strongly suggest using Onyx on a regular basis to help avoid this issue.

You can delete the corrupted .plist files (if you know how to find them) and let the OS or app rebuild them. But as indicated before you should take your rig to Apple for servicing.

I've had a crash course in Mac housekeeping this weekend Robert so something good has come out of all this. I'll pick up Onyx too whilst I'm at it. I've stuck these two plists (scheduler and version) into the trash.
I've found a similar issue on a mac site (apple board) - recommended updating the mac OSX combo 10.4.11 then if necessary going down the archive and install route (one step behind a full osx reinstall I guess?). There's also a recommended prog called Applejack.

At the very least I'll be armed with a bunch of ticked off boxes when/if I do take the machine to apple.
Cheers again.

i've been following this post with gritted teeth and an eye twitch... it has convinced me to look more into 'housekeeping', but has also confirmed my impending purchase of a second computer as an insurance policy. i want no longer to be held hostage by the whims of Compressor, or by the bugs of updates etc. the digital motto of 'if you don't have it in two places (or more...), you don't have it' seems to apply to the NLE program and machine, as well as storage...

Although it's never a bad idea to have 2 machines on-hand in case of a serious hardware issue, it might be overkill for your situation.

The best methodology for keeping everything stable is to not only maintain the system routinely (just as you would your car or home) but keeping physically separate backups of your OS and saved projects on external HDD's that are stored. When you have a stable-running system you should image the OS/apps/boot drive at least once every 2 weeks (more if you have the time) that way you always have a copy of a stable OS ready to be restored at a moments notice in case of the worst-case scenario. See my sticky thread about how to image your OS and restore it.

Indeed Robert. I learned the hard way this weekend, although fortunately now back on track - a smooth running system it seems, fingers crossed - looks like Disk Warrior (which has been fantastic btw) did indeed route out rogue files (plists - version and scheduler).
Will 'housekeep' on a weekly basis now and follow Robert's OS thread, picking up a few more drives as and when (are USB usually ok for OS/boot drives?).