Unsolicited NFS notification causing panic?

[LoH]

I've been trying to debug a server running FreeBSD 7.2-RELEASE/amd64 
that's hanging intermittently or rebooting without much luck.

The machine hosts the home directories for the users over NFS. The 
workstations that use it are pretty much all Solaris 10 boxes (mostly 
sparc with five x86 installs), with between two and five Solaris 8 
machines. The same machine is also a CUPS print server, which merely 
takes print requests and forwards them to networked printers. The 
machine had been running for about three weeks before exhibiting these 
problems (I had tinkered with using the RARP daemon, but have since 
reloaded the OS in an attempt to make sure my tinkering hadn't left any 
lasting damage).

The only messages I'm getting from /var/log/messages are like the ones 
below (the last message sent before the machine went down and rebooted).
Sep 17 13:54:32 <server> rpc.statd: Unsolicited notification from host 
<hostname>

The machine itself is a Dell PowerEdge 2900, and the HDDs are three 1TB 
drives in RAID5 (two virtual HDDs).

Any ideas as to what could be causing this? Our next test is to do a 
complete backup of the NFS partition onto a separate machine (different 
hardware) and test that one with a near-identical setup to screen for 
hardware problems.

--Joseph Lenox