There are many things that could be causing it.

1) buffer overflow in memory can cause a hang. I've seen it.
2) Bad hardward like faulty CPU.
3) Faulty disk
4) Faulty memory

Are you sure that you have full latest patches on your system?

Also, are you sure that you have good compatibility with your applications and OS?

Please do some diagnostic work and also check with your vendor site for compatibility. And if you have tech support get someone on your box to look around after you check the hardware.