Finally got BB and having been using this new ISP provided usb modem for about a week now with no probs. But today on boot up I got a blue screen with the legend "Driver IRQL not less or equal" and a suggestion that newly or recently installed hardware was causing the conflict.
I rebooted using the last known good configuration and so got back in alright, but it reads like something I should fix before I find I can't get back in at all.
Aside from hardware the only other silliness I've been doing is installing and updating the games utility Punkbuster - which shouldn't relate at all.
From other comments on the web one of the causes of the "Driver IRQL not less or equal" error is that the usb modem is drawing more power than a standard usb pc connection wants to provide. However my usb modem is plugged into a hub with it's own power lead, so that shouldn't be a problem for me.
I've stuck a query in with the ISPs techs, but thought I'd ask if anyone here had expierienced this before (preferably solving it too).