5.4/amd64 console hang

[Rong-En Fan]

Hi,

I'm using a Pentium Xeon 3.2G * 2 running 5.3/5.4 amd54 RELEASE. Recently,
I have frequently hang, say 4 in 3 days. Originally, I'm using
5.3-RELEASE-p5 or so,
and it happens, so I decided upgrade to 5.4-RC1/RC2 and disable HTT in BIOS.
Somehow, I noticed that this situation happens more frequently after upgrade to
5.4-RC1/RC2. This is a Mail server running Postifx with clamd/amavisd and
apache2 with some webmail applications. All users home directory (toatl 10)
is mounted from another NFS server running 5.4-PRELEASE/i386.
I have few ddb output and kernel config here:
http://rafan.infor.org/tmp/5.4-hang/
I executes ps, show threads, show lockedvn. 

when console hangs, serial console does not response, front console,
I can use alt+f? to switch vty, caps/numlock led is fine, but keyboard does
not response. can break to ddb.

any suggestions?

Regards,
Rong-En Fan