Vista Business Blue Screen

Hi,

I am running Vista Business on a Dell C521, with a home network, (Draytek
Vigor 2800 router and Linksys Wireless G) and am sufferng a plague of Blue
Screens of Death usually, but not allways, whenever one of the the
following is done:-

1 Another machine connnects to the network via Cat5 cable.
2 Another machine connnects to the network via wireless
3 Windows mobile Smart phone connects via wireless
4 USB Memeory stick inserted into USB port
5 USB Microsoft Web cam inserted into USB port
6 Dell Axim PDA Connects

And sometimes it seems to do it just for the hell of it.

BSOD says its related to fwpkclnt.sys, which is the windows firewall i
beleive, i've tried turning it off but to no avail.

its driving me mad, so any ideas welcome

Thanks in advance

Nige