FC4 x86_64 dies with heavy SATA RAID load

[Mark Miksis]

I have the 3Ware 9500S-4LP (running RAID5) installed in a Dell Poweredge
1800 (dual EM64T Xeon, 7520 chipset).  With Fedora Core 4 installed,
everything seems fine at first glance.  However, after a period (many
minutes) of heavy disk I/O operations, the machine begins to slow and
then becomes completely unresponsive.  I get "APIC error on CPUn:
00(40)" in dmesg which may or may not be related.  Nothing is logged to
syslog when the failures occur.  I have tried booting with noapic and
using the uP kernel.  Some of these configurations make the APIC error
go away, but the hangs still occur.  This machine will run fine for days
or more at high CPU loads as long as the I/O load to the RAID card is low.

Any thoughts?  Anyone running this configuration?