Hardware issues?

[esheesle]

I run a Freebsd 6.2 server. Lately I've been getting a lot of the following 
type errors:

Sep 20 20:01:54 rogue kernel: swap_pager: indefinite wait buffer: bufobj: 0, 
blkno: 165918, size: 12288

The system has a raid 0 setup. I thought the normal cause of this was a hard 
drive issue so I did some checking over the past couple of weeks. I did a bios 
based scan of both drives, checked the raid reports and it thinks they are 
fine. I also installed smartctl and do daily testing and it reports the drives 
are both fine.

It seems like I start getting those messages after the system has been up for 
a week or two. If i reboot they go away for several more days. Any thoughts on 
what could case this? The hardware is only 2 years old so the system isn't be 
overwhelmed. Showing 1% or less of processing via top at any given time.  Is 
the hard disk the only likely cause?

Thanks