Today I find XP to be getting harder and harder to support. Drivers are now lagging for fixes so while this sounds like a driver issue I strongly suggest you go back to when it worked WITHOUT the VZ wireless USB device.
Now back to when it worked talk to Verizon about their MIFI devices. More at http://news.cnet.com/8301-17938_105-10235202-1.html
I recently purchased Verizon wireless 5G internet device. Download and connection to internet went fine. After I connected the Verizon device to the Dell USB port though, it killed my other USB connections. I have 6 USB ports. Printer nor anything else would respond. Once I disconnected the Verizon wireless device, then rebooted, the other devices worked fine. I tried all different USB configurations with the Verizon device and other USB connected devices. Always the same issue. I can use multiple other USB ports/devices at the same time, just not with the Verizon device connected. Verizon Tech support has no clue. Dell wants my credit card number to even talk to a real person. Please help. I am running Windows XP SP3