system crash

[Tom Dempsey]

I have been experiencing frequent system crashes over the past two 
weeks.
-G4iMac 1 Ghz 768RAM -  Mac os 10.3.2

I think, but I'm not sure, that the crashes started when I was using 
Digital Performer 4.12 but now every application crashes eventually.  I 
installed DP4 at the beginning of January and things were fine for 3 
weeks.

I have run Disk Utilities from the installer disk but it usually 
crashes during repair permissions.

I have run Cocktail to repair permissions and that usually crashes.

I have dumped my cache files.

I have logged in as a different entity but the system crashes 
eventually.

Crash formats have been:
Application unexpectedly quit
Gray veil with restart method
Freezing with a spinning rainbow ball
Freezing with white text on black - says "error: unaligned stack"

These can happen at anytime and within any program - though it seems 
that DP4 and iPhoto are the least stable.

My work in DP4 has only been short MIDI sequences - under two minutes 
and less than six MIDI tracks, nothing fancy.. Usually these files are 
in the  100K - 500K size. However, one six track MIDI file is 2.1MB. Is 
this file size and anomaly and if so could it be the reason for the 
crashes?

I have discussed this recently on a Mac OSX list but until now none of 
the suggestions offered have helped.

Thanks
Tom in Skopelos Greece