Linux System Freeze

Over 10+ years I've had various kenel versions running on various hardware configurations with very little problem. I recently set up the following on 2 machines:

(1) Oracle Enterprise Linux (Redhat variant) Kernel 2.6.9-55.0.0.0.2.ELsmp on an AMD Athlon 64 Dual Core 4.2 Ghz processor with 1 gig RAM

(2) Oracle Enterprise Linux Kernel 2.6.9-67.0.0.0.1.EL on AMD Athlong 2.2 Ghz processor with 1 Gig RAM

These machines serve the following purpose:

Machine (1) runs Oracle Application Server 10gR2.
Machine (2) Runs Oracle 11g Database.

Since configuring these in January I've experienced systems freezes on both of them. The machine becomes totally non-responsive, isn't susceptible to a graceful shutdown using the Alt-SysRq-R-E-I-S-U-B key sequence and I'm left with no choice but the hard reset.

I can't find anything useful on Oracle's techsite or Google. As stated before I've had several installations of Linux running over the years, some much lesser hardware also running an Oracle database, with no significant issues.

No doubt the Oracle stuff is CPU/RAM intensive but I've got plenty of swap set up.

I suppose I could shutdown Oracle processes on both machines to see how long the machines will stay up. Before I did this I wanted to see if anyone had experienced similar issues with Linux. Plus since the freezes are intermittent and sometimes many days between occurences I'm not sure how much info I could glean from shutting down Oracle.

The only difference I can think of between my current installations and installations from prior years is the chipset. This is the first time I've installed Linux on AMD.

Anyone had experience with Linux on AMD? Or anyone exerpience similar behavior with Linux on any hardware platform?

TIA.