[CentOS] segfaults with 8 gig of ram

Hello All.
I have five Centos 4.4 x86_64 (amd fx-62) boxes with
4 gig of Corsair dual channel ram running
kernel 2.6.9-42.0.10.EL (smp).

The sixth box is the same except for video card and ram.
It is using 8gig of GSkill dual channel ram and has
a very cheap ATI video card in it.  This box will segfault
on boot unless I use noapic acpi=off and nolapic.  Even
with these boot params, the box is not 100% stable.  I have
seen udev segfault right when booting and also when copying
15 meg files from /tmp to /usr will lock things up sometimes.
Yum and Perl have gotten corrupted as well at different times.
I have 5 fans in the box to vent heat and the BIOS reports
the CPU running around 90 degrees Farenheit when rebooting.

I have run memtest86 (from Knoppix 5.1) all night long on the
8 gig of ram and it comes up OK.  In the past, we have found
problematic Corsair ram this way.  This 8 gig seems to be
OK as far as memtest thinks.

Today I will begin removing ram and testing to see what
happens.  Does anyone have some ideas what might be the
problem?  All the other five boxes with Corsair ram work
fine.

Thanks