svchost.exe problems

Hi all, new to the forum. Looking for help on a problem.

I noticed that after startup, my system takes a long time to become usable (10 min or so). During this time, both cores of the CPU are running at 100%. I've determined that this usage is caused by several instances of svchost.exe. This also happens if I do anything with networking (like changing wireless networks or disabling/enabling network cards). I've done numerous google searches and have yet to find anything very useful. Here is what I've tried so far:

-Full system scans of Avast anti-virus, Malwarebytes, Super Anti-spyware, and Hitman Pro. No major issues, mostly just tracking cookies. No change.
-Tried a clean boot as per instructions on Microsoft website. No change.
-If I boot into Safe Mode, the problem disappears, but if I boot into Safe Mode with Networking, the problem returns.
-I have an ethernet card and a Wireless card installed. If I disable one or the other, there's no change, but if I disable both at the same time, the problem disappears.
-I've located and installed the most up-to-date drivers I can find for both cards, no change.
-I used Process Explorer and looked up the Stack for the threads running with the highest CPU usage and found that the common file in almost all of them is ntoskrnl.exe

I'm sure there's something that I missed.

Sorry for the long post, just trying to give as much info as possible. Any help would be greatly appreciated.

I believe multiple SVChosts are common, if not necessary-- my Win7 64bit install has three running currently. I heard of this problem elsewhere, and the solution was removing a buggy network driver. Might want to look for those?