crash in in6_cksum

["Arne H. Juul" <arnej%pvv.ntnu.no@localhost>]

I'm unable to boot a current kernel on my NetBSD/i386 machine, it crashes 
with panic "in6_cksum: mbuf too short for IPv6 header" at stack:

#0  0xc04fab82 in cpu_reboot ()
#1  0xc0456593 in panic ()
#2  0xc0189e64 in in6_cksum ()
#3  0xc0184cbc in icmp6_input ()
#4  0xc0191812 in ip6_input ()
#5  0xc0191b2f in ip6intr ()
#6  0xc043d279 in softint_dispatch ()
#7  0xc0100e4d in Xsoftintr ()
#8  0x00000000 in ?? ()

the netbsd.old kernel that I'm now running on again is:

NetBSD inngang 4.99.53 NetBSD 4.99.53 (GENERIC) #3: Thu Feb  7 13:26:30 
CET 2008  root@inngang:/usr/obj/sys/arch/i386/compile/GENERIC i386

while any newer GENERIC kernels I've tried to build crashes.
Any hints?

  -  Arne H. J.