kassert panic in geom_journal

Hi,
I'm currently experiencing the same panic every now and then, which
has is origin in geom_journal:
 panic: poffset=635104768 plength=16384 coffset=635036672
It is triggered by a KASSERT ("Be sure that bios queue is sorted.") in
sys/geom/journal/g_journal.c:1033.
I use -CURRENT with WITNESS and INVARIANTS as of December 16th on a
Lenovo Thinkpad T400.
This KASSERT is triggered by "make buildworld buildkernel" or by building ports.

A kernel dump is available for further digging. Backtrace:
http://sites.google.com/site/lwfreebsd/Home/files/gjournal-backtrace.txt
Kernel config: http://sites.google.com/site/lwfreebsd/Home/files/kernel-CURRENT.txt
dmesg: http://sites.google.com/site/lwfreebsd/Home/files/dmesg-T400-FreeBSD-CURRENT.txt

Merry Christmas

Lucius