Panic on 5.2.1-R, netisr related?

(kgdb) info threads
(kgdb) info stack
#0  doadump () at ../../../kern/kern_shutdown.c:240
#1  0xc0633908 in boot (howto=260) at ../../../kern/kern_shutdown.c:372
#2  0xc0633bf8 in panic () at ../../../kern/kern_shutdown.c:550
#3  0xc06757e1 in bremfreel (bp=0xca91b178) at ../../../kern/vfs_bio.c:647
#4  0xc0675715 in bremfree (bp=0x0) at ../../../kern/vfs_bio.c:629
#5  0xc06791c4 in getblk (vp=0xc312ab2c, blkno=1, size=16384, slpflag=0, 
slptimeo=0, flags=0)
    at ../../../kern/vfs_bio.c:2468
#6  0xc06758b2 in breadn (vp=0xc312ab2c, blkno=0, size=0, rablkno=0x0, 
rabsize=0x0, cnt=0, cred=0x0, bpp=0x0)
    at ../../../kern/vfs_bio.c:700
#7  0xc067585c in bread (vp=0x0, blkno=0, size=0, cred=0x0, bpp=0x0) 
at ../../../kern/vfs_bio.c:682
#8  0xc0766d75 in ffs_balloc_ufs1 (vp=0xc312ab2c, startoffset=0, size=15680, 
cred=0xc19ced80, flags=65536,
    bpp=0xd1e078c0) at ../../../ufs/ffs/ffs_balloc.c:140
#9  0xc077f5e7 in ffs_write (ap=0xd1e078f8) 
at ../../../ufs/ffs/ffs_vnops.c:698
#10 0xc078a6d4 in dqsync (vp=0xc3149410, dq=0xc30bc140) at vnode_if.h:432
#11 0xc078a010 in qsync (mp=0xc2f03000) at ../../../ufs/ufs/ufs_quota.c:775
#12 0xc077de5d in ffs_sync (mp=0xc2f03000, waitfor=2, cred=0xc19bde80, 
td=0xc08ed960)
    at ../../../ufs/ffs/ffs_vfsops.c:1204
#13 0xc068ad4e in sync (td=0xc08ed960, uap=0x0) 
at ../../../kern/vfs_syscalls.c:141
#14 0xc0633505 in boot (howto=256) at ../../../kern/kern_shutdown.c:281
#15 0xc0633bf8 in panic () at ../../../kern/kern_shutdown.c:550
#16 0xc07dbb3c in trap_fatal (frame=0xd1e07b18, eva=0) 
at ../../../i386/i386/trap.c:821
#17 0xc07db802 in trap_pfault (frame=0xd1e07b18, usermode=0, eva=12) 
at ../../../i386/i386/trap.c:735
#18 0xc07db42d in trap (frame=
      {tf_fs = -1046347752, tf_es = 16, tf_ds = -1063124976, tf_edi = 28, 
tf_esi = 0, tf_ebp = -773817488, tf_isp = -773817532, tf_ebx = 0, tf_edx = 0, 
tf_ecx = 0, tf_eax = 972, tf_trapno = 12, tf_err = 0, tf_eip = -1067013504, 
tf_cs = 8, tf_eflags = 66050, tf_esp = -1046426856, tf_ss = -1046425884}) 
at ../../../i386/i386/trap.c:420
#19 0xc07cdf28 in calltrap () at {standard input}:94
#20 0xc06bc865 in icmp_error (n=0xc1a24700, type=0, code=3, dest=0, 
destifp=0x0) at ../../../netinet/ip_icmp.c:208
#21 0xc06cf9c3 in udp_input (m=0xc1a24700, off=20) 
at ../../../netinet/udp_usrreq.c:402
#22 0xc06bdf15 in ip_input (m=0xc1a24700) at ../../../netinet/ip_input.c:989
#23 0xc06a47ce in netisr_processqueue (ni=0xc08f5db8) 
at ../../../net/netisr.c:152
#24 0xc06a4ba3 in swi_net (dummy=0x0) at ../../../net/netisr.c:257
#25 0xc0621902 in ithread_loop (arg=0xc19ce580) 
at ../../../kern/kern_intr.c:544
---Type <return> to continue, or q <return> to quit---
#26 0xc0620a5e in fork_exit (callout=0xc06217a0 <ithread_loop>, arg=0x0, 
frame=0x0) at ../../../kern/kern_fork.c:793
(kgdb)

sysctl.conf:
kern.ipc.somaxconn=1024
kern.maxfiles=102400
kern.maxfilesperproc=10240
#net.isr.enable=1
net.inet.tcp.inflight_enable=1
net.inet.tcp.syncookies=0

Kernel config attached. I do realise that my configuration and kernel source 
is not exactly supported, but I'm not sure this is related to ALTQ - even if 
so, maybe this will help Max avoid a possible problem before ALTQ gets 
merged.

-- 
   ,_,   | Michael Nottebrock               | lofi_at_freebsd.org
 (/^ ^\) | FreeBSD - The Power to Serve     | http://www.freebsd.org
   \u/   | K Desktop Environment on FreeBSD | http://freebsd.kde.org