Random freezes on AMD X2 when multiprocessing enabled

[Hunter McDaniel]

Configuration summary: ASUS A8V motherboard (socket 939), AMD 3800 X2 
dual core processor,  nVidia 5500 AGP video card, 1 GB DDR400 memory

I've installed Fedora 8 twice on this machine, both the i686 and x86_64 
versions and had the same result both ways.  The machine boots up fine, 
but within a minute or two after logging on to Gnome (I haven't tried 
KDE) I will get a hard freeze - mouse pointer freezes, no response to 
keyboard (including CTRL-ALT-F1), and pings to the machine go 
unreturned. Adding 'nosmp' to the kernel boot options makes the problem 
go away, but that's a bit like having an SUV that conks out and has to 
be towed if you engage 4WD.

FWIW, booting from the x86_64 live CD gives pretty much the same 
symptoms - hard freeze within a minute or so after logon.  With the i686 
live CD I can't even get through startup - the machine freezes right 
after getting an OK from the Starting udev.... step.

I've been running previous Fedora releases (back to FC5 at least) on 
this machine for years with smp enabled without ever having any problems 
like this, so I don't THINK it's a hardware issue.  Still, I haven't 
seen anyone else post similar symptoms so I have to wonder.  I've seen 
some references to freezes with the nvidia binary drivers, but that's 
not my problem - I only have the default 'nv' drivers.

I've tried a couple of other boot options that seemed like they might be 
relevant - noapic, nomce - but neither one made any difference.

I'd appreciate any suggestions on
a) what I should try next
b) other diagnostic information that would be useful
c) other places I should ask

Thanks