2.5.9 (latest bitkeeper, to be precise) dumps this message into
/var/log/messages within a few minutes after startup. Running xmms or
mozilla seems to do the trick. I ran two of the messages through
ksymoops and attach the results here, in case they are meaningful. 
I'll be happy to help debug it further, if necessary. 

Here's one such message: 

Jul 28 22:28:54 tea kernel: bad: schedule() with irqs disabled!
Jul 28 22:28:54 tea kernel: cdf99cb0 c0275680 cf742580 cdf99cd8 c010fbf4 00000001 00000082 00000005 
Jul 28 22:28:54 tea kernel:        c02ffbd8 fffffffa cdf99ce8 c010fc0b cf742580 00000000 00000246 c0117b5f 
Jul 28 22:28:54 tea kernel:        cdf98000 00000001 00000005 c0226170 c021a359 00000000 c032cbf8 cf72ea60 
Jul 28 22:28:54 tea kernel: Call Trace: [<c010fbf4>] [<c010fc0b>] [<c0117b5f>] [<c0226170>] [<c021a359>] 
Jul 28 22:28:54 tea kernel:    [<c01cf5e2>] [<c022507f>] [<c0226170>] [<c01e7195>] [<c01ebad6>] [<c0239488>] 
Jul 28 22:28:54 tea kernel:    [<c023420c>] [<c0234c77>] [<c022ac87>] [<c01257d5>] [<c0110480>] [<c0126500>] 
Jul 28 22:28:54 tea kernel:    [<c0246428>] [<c020c432>] [<c01103ab>] [<c010ee05>] [<c020c629>] [<c0135886>] 
Jul 28 22:28:54 tea kernel:    [<c0117dec>] [<c013597a>] [<c0106fff>] 

And here are two of them passed through ksymoops: 

mulix@tea:~$ ksymoops -m /boot/2.5-mx/System.map < ~/tmp/oops2
ksymoops 2.4.4 on i686 2.5.29.  Options used
     -V (default)
     -k /proc/ksyms (default)
     -l /proc/modules (default)
     -o /lib/modules/2.5.29/ (default)
     -m /boot/2.5-mx/System.map (specified)

cdf99cb0 c0275680 cf742580 cdf99cd8 c010fbf4 00000001 00000082 00000005 
        c02ffbd8 fffffffa cdf99ce8 c010fc0b cf742580 00000000 00000246 c0117b5f 
        cdf98000 00000001 00000005 c0226170 c021a359 00000000 c032cbf8 cf729660 
Call Trace: [<c010fbf4>] [<c010fc0b>] [<c0117b5f>] [<c0226170>] [<c021a359>] 
   [<c01cf5e2>] [<c022507f>] [<c0226170>] [<c01e7195>] [<c01ebad6>] [<c0239488>] 
   [<c023420c>] [<c0234c77>] [<c022ac87>] [<c0126500>] [<c0246428>] [<c020c432>] 
   [<c020f7d3>] [<c010ee05>] [<c020c629>] [<c0135886>] [<c0117dec>] [<c0117d24>] 
   [<c0117b1b>] [<c013597a>] [<c0106fff>] 
Warning (Oops_read): Code line not seen, dumping what data is available

Trace; c010fbf4 <try_to_wake_up+144/150>
Trace; c010fc0b <wake_up_process+b/10>
Trace; c0117b5f <do_softirq+8f/a0>
Trace; c0226170 <ip_queue_xmit2+0/210>
Trace; c021a359 <nf_hook_slow+169/190>
Trace; c01cf5e2 <__elv_add_request+12/20>
Trace; c022507f <ip_queue_xmit+45f/4b0>
Trace; c0226170 <ip_queue_xmit2+0/210>
Trace; c01e7195 <ata_set_handler+75/90>
Trace; c01ebad6 <idedisk_do_request+456/670>
Trace; c0239488 <tcp_v4_send_check+78/c0>
Trace; c023420c <tcp_transmit_skb+55c/610>
Trace; c0234c77 <tcp_write_xmit+157/290>
Trace; c022ac87 <tcp_sendmsg+f67/1250>
Trace; c0126500 <filemap_nopage+f0/1e0>
Trace; c0246428 <inet_sendmsg+38/40>
Trace; c020c432 <sock_sendmsg+72/90>
Trace; c020f7d3 <alloc_skb+d3/1a0>
Trace; c010ee05 <do_page_fault+1a5/4b5>
Trace; c020c629 <sock_write+99/b0>
Trace; c0135886 <vfs_write+b6/140>
Trace; c0117dec <bh_action+1c/30>
Trace; c0117d24 <tasklet_hi_action+44/70>
Trace; c0117b1b <do_softirq+4b/a0>
Trace; c013597a <sys_write+2a/40>
Trace; c0106fff <syscall_call+7/b>


1 warning issued.  Results may not be reliable.
mulix@tea:~$ ksymoops -m /boot/2.5-mx/System.map < ~/tmp/oops
ksymoops 2.4.4 on i686 2.5.29.  Options used
     -V (default)
     -k /proc/ksyms (default)
     -l /proc/modules (default)
     -o /lib/modules/2.5.29/ (default)
     -m /boot/2.5-mx/System.map (specified)

cdf23cd4 c0275680 cf742580 cdf23cfc c010fbf4 00000001 00000096 00000001 
c02ffbd0 fffffffc cdf23d0c c010fc0b cf742580 00000000 00000246 c0117b5f 
cdf22000 00000001 00000003 c0226170 c021a359 00000000 c032cbf8 00000002 
Call Trace: [<c010fbf4>] [<c010fc0b>] [<c0117b5f>] [<c0226170>] [<c021a359>] 
c022507f>] [<c0226170>] [<c0239488>] [<c0239488>] [<c023420c>] [<c020f7d3>] 
c02366d1>] [<c020f99b>] [<c022be04>] [<c02463d9>] [<c020c481>] [<c01c1ba3>] 
c01c0830>] [<c020c585>] [<c0135746>] [<c0117dec>] [<c013593a>] [<c0106fff>] 
Warning (Oops_read): Code line not seen, dumping what data is available

Trace; c010fbf4 <try_to_wake_up+144/150>
Trace; c010fc0b <wake_up_process+b/10>
Trace; c0117b5f <do_softirq+8f/a0>
Trace; c0226170 <ip_queue_xmit2+0/210>
Trace; c021a359 <nf_hook_slow+169/190>


1 warning issued.  Results may not be reliable.

-- 
http://vipe.technion.ac.il/~mulix/
http://syscalltrack.sf.net/