Kernel panic - never had one before, what do I do?

I just got a panic. As I have never had one before, I don't know what to 
do. It's on another system so I don't have to reboot immediately (that 
would solve the problem temporarily, wouldn't it?) if someone would give 
me some advice, I could try to help debug it; however, as I'm not a 
coder (not a real one anyway), I don't know how much help I would be.

It's a 5.0-CURRENT system, just installed and built last week. It 
paniced right after doing a source update (not a build, just cvsup). 
The panic error is as follows:

panic: mtx_lock() of spin mutex vnode interlock _at_ 
/usr/src/sys/kern/vfs_subr.c:3187

Thanks,
Jason