I had the same problem with the svchost.exe network service using 100% of the cpu time for a few minutes when initially started. I'm using Windows XP Home. This happen when I connected to the internet (using DSL) and tried to access it by starting the browser or any other program that tried to use the internet. After what seemed forever, once svchost.exe network service had finished loading whatever it was loading, it was fine from then on for using the internet. For my case I tracked it to having a large HOSTS file. I had a large HOSTS file, which I downloaded from SpyBot and other sites to help block ads, etc. My final HOSTS file was 925 KB. I even tried a smaller 375 KB HOSTS file with out any luck. It wasn't until I used a HOSTS file of 46 KB that the time to connect was returned to a reasonable fast time. I hope this helps someone, since my search of the Internet on this problem didn't find anything.