panic: driver error: busdma dflt_lock called

[Karim Nogas]

Hello,

I was wondering if someone could explain this error message, and where I 
should look for a resolution.

I installed FreeBSD 6.1, configured my NIC, and was using it for a 
couple days without problems.  Now, even after a fresh install, I keep 
getting this error.  The only resolution I've found is to login in 
Single-User Mode, run fsck, and mount -a.  Unfortunately, this 'fix' is 
temporary as the problem occurs again with a reboot.

Any ideas would be greatly appreciated.  Thank-you.