kernel panic

Hi,

One of our OES2-SP1 servers (fully patched) had the
following kernel panic and crashed:

Jun 23 00:33:00 rufus kernel: NSS Free Tree(3) is corrupt.
Jun 23 00:33:00 rufus kernel: ASSERTION FAILED
Jun 23 00:33:00 rufus kernel: File is:
/usr/src/packages/BUILD/nss/modules-build/linuxmpk/mpkmisc.c
Jun 23 00:33:00 rufus kernel: Line Number is: 358
Jun 23 00:33:00 rufus kernel: ----------- [cut here ] --------- [please
bite here ] ---------
Jun 23 00:33:00 rufus kernel: Kernel BUG at
....packages/BUILD/nss/modules-build/linuxmpk/nwcore.c:204
Jun 23 00:33:00 rufus kernel: invalid opcode: 0000 [1] SMP
Jun 23 00:33:00 rufus kernel: last sysfs file:
/devices/pci0000:00/0000:00:11.0/subsystem_device
....

Any ideas, what could be the reason?

Thanks
Bernhard