Sierra wireless modem crashes computers

I have Sierra USB modem and Sprint mobile broadband. It worked fine for a few days, but now my computer crashes when I try to connect. I get the ''blue screen of death'' and a page fault error.

It's happened with two different laptops, a Dell and an Acer. (Both running WinXP.) I think it's a power issue, because it only happens if the computers are running off battery. If they are plugged in, everything's fine.

I tried removing all other USB devices, unchecking ''Allow the computer to turn off this device to save power''under the Power Management settings for the USB Root Hub entries, and reinstalling the USB and Sierra drivers, butit didn't help.