what operations are you perfoming when it crashes?
I also have problem with programs crashing on my mac's but so far not with maya. but normally when I am using a program that is memory intensive.
I recently bought a powermac g4 dual processor and maxed out the memory, so far that seems to have solved my problems with the programs that I had problems with... But only time will tell.
Not suggesting getting a new computer is the answer but upping your memory could be a solution.
Have you experienced this with other programs?
I still haven't found the cause for my shutdowns... But I am still looking, not that I am an expert in any way, just don't like not knowing the answer.
Would you mind giving me more details so I can compare them with my own?
Maybe we'll find the answer
I hope this helps