Kernel core dump in recent 4.8-STABLE

[Daniela]

Today my system coredumped (4.8-STABLE from Saturday), I believe it's somehow 
X11 related:

X11 crashed first (signal 11). I was running it as root (I know I shouldn't).
I didn't think about it and restarted X11. While it was starting, I had a look 
at the console, there was a bright white message: issignal.
This shows up at X11 startup.
Then the system coredumped.

Below is more information. Is this a serious problem?
Please help me, I'm an inexperienced programmer and I can't do this alone.

Daniela



# gdb -k kernel.debug vmcore.0
...

IdlePTD at phsyical address 0x005ba000
initial pcb at physical address 0x004d3100
panicstr: ufsdirhash_lookup: bad offset in hash array
panic messages:
---
panic: ufsdirhash_lookup: bad offset in hash array

syncing disks... 80 2 1
done
Uptime: 1d21h53m1s
/dev/vmmon: Module vmmon: unloaded

dumping to dev #ad/0x30001, offset 1048704
dump ata0: resetting devices .. done
511 ... 0
---
#0  dumpsys () at /usr/src/sys/kern/kern_shutdown.c:487
487             if (dumping++) {
(kgdb) where
#0  dumpsys () at /usr/src/sys/kern/kern_shutdown.c:487
#1  0xc021f00b in boot (howto=256) at /usr/src/sys/kern/kern_shutdown.c:316
#2  0xc021f449 in panic (
    fmt=0xc0433ba0 "ufsdirhash_lookup: bad offset in hash array")
    at /usr/src/sys/kern/kern_shutdown.c:595
#3  0xc033b1d3 in ufsdirhash_lookup (ip=0xc262eb00,
    name=0xd804c427 
"kufacts.cc.ukans.edu_ftp_pub_history_Europe_Medieval_aids_FFFFFF_4dbcef50", 
namelen=73, offp=0xc262eb64, bpp=0xd8d2ecbc, prevoffp=0x0)
    at /usr/src/sys/ufs/ufs/ufs_dirhash.c:361
#4  0xc033589d in ufs_lookup (ap=0xd8d2ed18)
    at /usr/src/sys/ufs/ufs/ufs_lookup.c:212
#5  0xc033aa31 in ufs_vnoperate (ap=0xd8d2ed18)
    at /usr/src/sys/ufs/ufs/ufs_vnops.c:2376
#6  0xc0248a8e in vfs_cache_lookup (ap=0xd8d2ed70) at vnode_if.h:77
#7  0xc033aa31 in ufs_vnoperate (ap=0xd8d2ed70)
    at /usr/src/sys/ufs/ufs/ufs_vnops.c:2376
#8  0xc024b9f9 in lookup (ndp=0xd8d2eec8) at vnode_if.h:52
#9  0xc024b4f4 in namei (ndp=0xd8d2eec8) at /usr/src/sys/kern/vfs_lookup.c:153
#10 0xc0253f3f in vn_open (ndp=0xd8d2eec8, fmode=1, cmode=0)
    at /usr/src/sys/kern/vfs_vnops.c:138
#11 0xc0250074 in open (p=0xd8b87f20, uap=0xd8d2ef80)
    at /usr/src/sys/kern/vfs_syscalls.c:1029
#12 0xc03c25b5 in syscall2 (frame={tf_fs = 134676527, tf_es = 47,
---Type <return> to continue, or q <return> to quit---
      tf_ds = -1078001617, tf_edi = 4, tf_esi = 686954328,
      tf_ebp = -1077941708, tf_isp = -657264684, tf_ebx = 686871084,
      tf_edx = 0, tf_ecx = 15, tf_eax = 5, tf_trapno = 12, tf_err = 2,
      tf_eip = 686596376, tf_cs = 31, tf_eflags = 663, tf_esp = -1077941752,
      tf_ss = 47}) at /usr/src/sys/i386/i386/trap.c:1175
#13 0xc03b30a5 in Xint0x80_syscall ()
#14 0x28ee321f in ?? ()
#15 0x2920f154 in ?? ()
#16 0x292036ea in ?? ()
#17 0x291fbd7d in ?? ()
#18 0x291fbc8f in ?? ()
#19 0x29200061 in ?? ()
#20 0x281b434b in ?? ()
#21 0x281b05e4 in ?? ()
#22 0x291f9d97 in ?? ()
#23 0x804ccba in ?? ()
#24 0x804d9c0 in ?? ()
#25 0x804de1c in ?? ()
#26 0x804ec0e in ?? ()
#27 0x804b42e in ?? ()