Thanks for advises.

Now, I'm running kernel with POOL_DIAGNOSTIC option hinted by advise
from Tobias Nygren.

And I noticed that the problem might related to swap/paging activity.

Currently top(1) shows:

load averages:  1.15,  1.19,  1.16                  up 0 days,  1:29   17:17:15
76 processes:  1 runnable, 73 sleeping, 1 stopped, 1 on processor
CPU states: 33.7% user,  0.0% nice, 39.6% system,  0.5% interrupt, 26.2% idle
Memory: 591M Act, 277M Inact, 1072K Wired, 33M Exec, 701M File, 40M Free
Swap: 2048M Total, 2048M Free

Yes, no swap area is used.  The panic seems to happen when the
system's load become heavy, such as building kde3 packages.

Is there known problem related to swap/paging activity?

-- 
Takahiro Kambe <taca@back-street.net>