> >> I'd try a kernel compiled with nothing other than
> >> "-march=pentium4 -O2 -pipe" added.
> 
> >Running grep over a disassembly could be informative.
> 
> For what it's worth, I rebuilt the kernel with this, and it seems totally
> stable again, at least with auich.
> 
> So it appears that specifying sse can cause horrific weirdness.

sse or sse2? I haven't had any problems with the latter.