OK, I'm lost at what's going on. I've installed redhat 6.2 with rpm upgrades on a box, and everything seemed OK. Now it randomly spits out

'Unable to handle kernel NULL pointer dereference at virtual address xxxxxx'

And a bunch of stuff about the stack, and various registers, etc.

I'd say there was something wrong with the kernel, but I've tried three different kernel rpms (now on 2.2.17-14) and have the same problem. We have another machine that's same kernel level and doesn't have problems. I don't think it's a kernel problem, but ...

There doesn't seem to be any order to the message. Different programs cause it, and sometimes it locks the box up while other times it doesn't - sometimes it causes a user program to die, other times it's caused the swapper to die.

I've looked around at various information around, and some tend to suggest that there's bad memory in the box. I tried to run memtest86 on it (the first 7 tests didn't find any problems - I was unable to run the extended tests at the time since the box couldn't be down the amount of time they required)

I don't know what else to do - does anybody have any ideas on what to even look at? I guess another step would be to contact Redhat for support - though there's enough extra stuff installed on the box, that I don't know how much help they'll be. Anyone have any experience with their support? Is it worth contacting them? Anyone have any a good experience with a support company and would recommend to use?

Thanks for any suggestions.