Alltel Only Stays Connected For 5 Minutes

I have a Dell Latitude D400 XP laptop. I connected my alltel UM175 modem into the COM3 USB port on the side, installed the software/driver.

Now when I go to connect, everything runs smoothly for about 5-8 minutes. After 5-8 minutes I cannot NAVIGATE THE INTERNET. Access says I'm still connected, but I can't navigate anywhere on the net. I have to reboot the laptop and get another 5-8 minutes. After that time, I have to reboot again.

If I am downloading a big file, I can stay connected for hours. I just got done downloading a game demo that was 678MB, took about 5 hours, and I never lost the connection. About 20 minutes into the download, I tried getting onto firefox AND internet explorer: I couldn't navigate. I couldn't even get GOOGLE to show up. Only a white screen.

I also have a Vista home premium 32-bit desktop, and I have 0 problems with alltel on it. I can navigate the internet for hours and never get a white screen.

Does anyone have any advice on why my XP laptop is being so difficult?

EDIT: I also have tried connecting my Xbox 360 to my desktop and sharing internet with alltel. Works great. But when I try it with my XP laptop, I can get on Xbox LIVE for about 5 or 6 minutes, then it says I lost the connection, even though Access says I'm still connected.

 

I'm wondering if the alltel connection times out after a period of time if the username and password isn't entered.

When I have the modem in my vista, I never have to worry about username or pass, but maybe that could be causing the problem with my XP?

Does anyone else have this problem?

 

No I do not have the LAN disabled that says "PANTECH UM175AL WWAN Driver" under it. Do you think that is causing the problem?

The only other LAN I have is the one I have my xbox 360 plugged into; which is the LAN port and driver that is installed on my laptop.

There is no other wireless LAN connection in my area, being that I live in the country.

 

Ok, disabled my LAN on the UM175.

Still having the same problem.