It's impossible to say.
You'll need to try pinpoint the problem. Usually this means trying with as minimal SW setup as possible. If the lockups happen even there, then it might be a HW problem.
However, if the minimal SW setup appears to work, then you can bring back components / patches / etc one at a time until the lockups return. Then go back again to verify that this particular item causes the problem.
If it's a HW problem then similar methods can be used for the problem isolation, too. Strip down the system to as bare minimum as possible. See if that works. If it doesn't, then some of these core components is having trouble, and in this case the only solution is to swap in known good components and see if any of those cures the problem.
However, if the minimal setup works, you can now start adding the expansions, zorro cards etc until the problem reappears. Then go back to verify that this particular component causes the problem.
Unfortunately these methods are not bulletproof, as sometimes problems can arise from combination of SW and/or HW components.
It helps a lot if you can find some method of reproducing the problem easily (say in minutes rather than hours). If the problem is elusive one and there is no easy way to reproduce it, it might be close to impossible to reliably track it down.
