I first noticed this around 2 weeks ago, I think, and it happened to me 
again last night... I did a shutdown -r now to reboot and my machine 
seemed to hang while killing off all the processes (or maybe while 
waiting for 'em to die or something). It only seems to happen if the 
machine's been up for a while though (maybe over a day or so). I went 
into ddb and got a stack trace, which showed functions in the VM system, 
such as vm_object_collapse (I think). I was in a hurry to reboot, so I 
didn't write down the trace.

So, I was wondering if anyone else has seen this? I'm currently running a
Jan 29 kernel, the last time I had the problem, I was running a kernel
from maybe about 3 weeks ago. The machine's a Pentium, 48MB RAM, 64MB of
swap space. 

I'll try to write down more detailed info the next time it happens...

Name: Dave Huang     |   Mammal, mammal / their names are called /
INet: khym@bga.com   |   they raise a paw / the bat, the cat /
FurryMUCK: Dahan     |   dolphin and dog / koala bear and hog -- TMBG
Dahan: Hani G Y+C 21 Y++ L+++ W- C++ T++ A+ E+ S++ V++ F- Q+++ P+ B+ PA+ PL++