Kernel problems on 5.3

[Jacob S]

Hello list,

Out of 3 new dell servers, one is having some instability problems in
the form of 2 kernel panics in less than a month. The problem server, in
this case, is also the server that averages a load of 4.0 - 9.0, while
the other two loaf around at 0.2.

The servers are running FreeBSD 5.3-RELEASE. Unfortunately, they're at a
Co-Lo facility, so I'm a little bit limited in what I can do to them
(everything's via ssh at this point). 

The only thing I can find in the logfiles that looks even remotely
related to the crashes is this line from /var/log/messages:

Mar  2 09:02:46 enterprise kernel: em0: discard frame w/o packet header

The servers are 2.8Ghz Xeons with 1GB of ram. The kernels are custom
compiled to enable smp/htt and quotas. I'm afraid I'm still a little bit
green with FreeBSD, even though I've been using Linux for 6 years now.
Does anyone have any suggestions for getting this server stable, or even
where to look for more troubleshooting info.?

TIA,
Jacob