Don't know what is causing your situation, but I think this might help. Go to »dslreports.com
, click on tools, scroll down to DRTCP, download DRTCP to your desktop, reboot computer.
Go back to dslreports/tools, and scroll down to tweak test.Run the tweak test and then follow instructions. You must have JAVA installed in order to run test. Hope this helps.
4G Verizon Wireless with Pantech UML290 USB modem, DRTCP, WinXP Pro, Dell Optiplex GX260 2.4 Mhz GB, 1536 MB memory.