BSOD from Outpost Firewall or Brother network printer?

Thanks to those who helped me previous located the debug info for my BSOD
problems. I've investigated some more and have the following info (I'm
running Vista Ultimate x32):

BSOD reports:

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DRIVER_IRQL_NOT_LESS_OR_EQUAL
STOP 0xD1 (0x650095, 0x2, 0x0, 0x83FC31B9F)

afd.sys

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WinDbg also reports:

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Probably caused by : afd.sys ( afd!AfdGetReceiveBuffer+58 )

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I hadn't had any BSOD problems until I installed the latest
(Vista-compatible) Outpost Firewall from Agnitum. It also seems as if the
BSOD happens when I print - although it may have happened at other times
(and my printer had been working fine for weeks).

I've disabled Outpost to see if that helps, but would appreciate any advice
as to how I could solidly determine that Outpost was at fault, or whether
it's something else.