*evenbiggersigh* Back up... again. This time (again) I think it should be ok (again).
A suspected faulty drive has been removed and the nice dual motherboard have been replaced with a slightly slower PIII-450 that was found. Assuming we're still up tomorrow (fingers crossed) that'll mean that the load problems have been fixed (they were causing crashing).
My huge thanks to Fred for troubleshooting and the spare hardware, and Tom (at the co-lo) for putting up with me keeping him there long after he should have been gone home and saving my bacon in a couple of cases (mkraid --dangerous-no-resync is your friend!).
Mail will be back up in a few minutes, as soon as I restore the mail spool from backup... some data (logs mostly it seems) was lost, so please email me if you find anything busted.
UPDATE: OMG! It's still up! Whohoooo!