Problem: svchost.exe was maxing out the CPU (under user name of Network Service) preventing connection to internet.
Culprit (well, at least one culprit): using very large hosts file from Supertrick suite to block ads in brower while DNS Client service is running.
Resolution: do ipconfig /flushdns to clear dns cache. Then, disable DNS Client service. Browser connects to internet perfectly, blocking ads with host file, and Svchost.exe not causing CPU maximum usage.
Read on further if needed...
In my case I was using a very large hosts file from the Supertrick suite to block ads from my browser. For the longest time the hosts file caused no problems. But one day I loaded my browser and couldn't connect to the internet.
The Task Manager showed svchost.exe with CPU usage of 99% and user name of Network Service. If I killed the task I could connect. But this was a pain in the ass. If I deactivated the host file I did not have the problem but got the ads in my browser.
The culprit wound up being the DNS Client service being on automatically and apparantly keeping cache of entries in very large hosts file. When I flushed the cache and disasbled the DNS Client the problem went away.
Hope this helps.