Partial success with bsd-airtools v0.3 on FreeBSD -CURRENT

I have a Linksys WCP11 card (Intersil Prism 2.5 chipset, flashed
with firmware Primary 1.1.1, Station 1.7.4). The FreeBSD on this
box is a very recent -CURRENT (no changes to the wi driver since 
the last cvsup).

dstumbler v0.3 seems to work just fine:

   ifconfig wi0 monitor up
   /opt/bin/dstumbler wi0 -o

I see two access points, as expected.
                                                                                Also, prism2dump does just fine: 

   /opt/bin/prism2ctl wi0 -m
   /opt/bin/prism2dump wi0

I see beacons as well as user data.

However, I've never managed to recover WEP keys using dwepdump 
and dwepcrack. The lack of success despite the amount of data 
gathered made my suspicious. While looking at the pcap files 
created by dwepdump with tcpdump -r , I see bogus packets without 
any IEEE 802.11 headers at all. 

Can anyone confirm that dwepdump from bsd-airtools v0.3 creates 
valid pcap files on FBSD-CURRENT to be used with dwepcrack? 
Are the pcap files between bsd-airtools and tcpdump (from CVS) 
supposed to be compatible?

TIA, Oliver