5.2-BETA lockup

Hi,

Since updating two of my machines to the latest HEAD I am experiencing a 
  total lockup on one of them.

After being booted for approx 3 minutes the machine stops responding 
completely. It doesn't panic or drop into DDB. The numlock key doesn't 
toggle the keyboard light, and I can't drop it into DDB manually.

I have full debugging options compiled in to this kernel as per the 
usual -CURRENT GENERIC file.

It's currently booted with the older kernel from the 16th and this is 
stable as a rock.

Anything else I can do to find the problem out or workaround it 
considering it just hangs?

The machine is a router running two 3com network cards (xl) and 
IPFW/natd. It also has IPV6 with IP6FW, and a gif tunnel.

Matt.