Kernel Panic with ZFS

My kernel just panicked. Here is what it said.

panic: kmem_malloc(131072): kmem_map too small: 167264256 total allocated
cpuid = 0
KDB: enter: panic
[thread pid 37 tid 100042 ]
Stopped at      kdb_enter+0x32: leave
db> :(


At the time this happened I was transferring lots of files to this 
system (personal file server) via the Apple File Protocol -- netatalk. 
It went fine for a few GB. Then this happened.

The reason I'm running current rather than stable is that ZFS is a 
selling point.(but opensolaris doesn't work for me...) I have a zpool 
with 2 hard drives and 1 partition of a slice of another disk that is 
shared with root and swap. Mirroring isn't on.

This farily old PC has a Pentium III Tualitin Celeron, and just 512MB of 
RAM. But the unrecommended minimum is 1 GB for ZFS. So I'm not sure if 
the problem is...

I'm out of RAM. But I watched the memory usage and it didn't go up. Swap 
wasn't touched at all.

Network related? Googling for the error I got got something I believe is 
unrelated.
Or something else. Anyway I'm leaving the machine on in case anyone 
could use a trace if it helps.

Thanks in advance!