Juan RP wrote:
> Why should it be a hw memory problem? I don't have such problems
> with NetBSD/i386 and Windows.

One possible explanation would be that you're using more RAM
when using Xen and the data will likely end up in different
parts of it. If you have more than a single RAM module you
could rip out as much as possible and see whether it still
crashes - which might be faster than trying memtest.

Another explanation could be that your system gets hotter
under Xen than without. It might not necessarily be a memory
problem. It could be the CPU, a controller, the chipset.

Of course, none of that can rule out a software bug either.

-- 
Christian