...that are using the "svchost.exe" service. (By the way, this Windows XP SP2 machine also has 4 instances of "svchost.exe" running, just like your's.)

Open the "Task Manager" again, then click on the "Processes" tab. See if any of the other programs which required their dll's to access the internet are causing a problem. You could try clicking on Start-Run, type "msconfig" (without the quotes), then clic on OK. When the System Configuration Utility loads, click on the "Start Up" tab and see if there are any "improper" programs that need to be UNCHECK so they don't run at start up. The link below should help you identify which ones are unnecessary:

http://www.sysinfo.org/startuplist.php

The link below should also help with a procedure to identify tasks that are being used by "svchost.exe":

A description of Svchost.exe in Windows XP

Because spyware/adware can cause this type of problem, make sure to download, install, update, then run the free spyware removal tools from the links below:

Ad-Aware">http://www.lavasoftusa.com/support/download/]Ad-Aware