Below I am posting lxp's response (which was via email), in case other N900 Kismet users are experiencing similar issues:
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I have analysed your pcap file and in combination to your bug
description, I think the problem is due to the driver somehow
misconfigures the wl1251's packet filtering in some special cases. My
patch doesn't touch that part of the driver because my tests showed it
works without modification (for me) so I haven't thought much about it.
I think the bug is triggered by either a special network type or
parameter of a network you connect to before going into monitor mode.
Maybe it is not only caused by a single network but a combination of
different networks if you usually use multiple networks before monitor mode.
It would be good if you could try to determine the network or even
better the parameter itself which causes the problem. At best you would
reboot after every network connect + monitor mode test to get a clean
state for the next try.
I would first suspect ad-hoc networks if you use any because I haven't
tested ad-hoc networking yet.
If you can determine a network which causes the problem, please tell me
the parameters of it:
* network type (infrastructure/ad-hoc),
* encryption type (open/wep/wpa-psk/wpa eap),
* hidden ssid (yes/no) and
* power management (full/half/off)
Maybe you can also suspect a network parameter for triggering the bug.
If you couldn't determine any single network which causes the problem I
think I have to build a debug driver for you, so we can tell for sure
your problem isn't caused by the packet filtering.