I have experienced kernel hangs w/ -current snapshots on Athlon 64 X2

and Sempron boxes.  Both GENERIC and GENERIC.MP snapshots exhibit the

hang.  Once hung, the boxes don't respond to pings; however, keyboard

LEDs toggle as expected and I can enter ddb from the keyboard.

kernel/5777 [1] has the full problem report including dmesgs and ddb

logs.  The hang is reproducible by building the eclipse-sdk port.
This problem has developed fairly recently (within the past month or

so).
A similar box (w/ Opteron 165) runs -current i386 GENERIC.MP snapshots

and is able to do the same port builds without hanging.  It seems the

forementioned kernel hang doesn't affect the i386 variant.
I would be happy to provide additional information that would help

analyze and resolve the problem.
[1]