User-mode Linux kernel port

Can't get UML pcap transport working
I want to build a Snort UML and so need to sniff an interface on my host machine.
I decided UML pcap transport would be best for this but can't get it to work.
Using a UML compiled from a vanilla 2.6.24.3 with the pcap transport option enabled during make menuconfig ARCH=um stage I get the following kernel panic :

Netdevice 1 (02:01:02:03:04:05) : pcap backend, host interface eth0
BUG: failure at mm/slab.c:592/page_get_cache()!
Kernel panic - not syncing: BUG!

My command-line config is :-
./linux umid=pcap \
ubda=pcap.cow,rootfs \
mem=128M \
eth1=pcap,eth3,tcp

Any pointers ?

Details
Host = Debian Etch on AMD64