Svchost problems

I recently switched my virus protection to Norton Internet security 2009 and ever since then I have had a problem.

The problem doesn't happen on every occasion but when it does it is a right pain.

The problem occurs when I try to load a cd/dvd, rip a cd or any similar function.

My PC freezes totally, the mouse freezes, the keyboard doesn't work and the only way I can solve the problem is by physically switched the PC off by pressing the reset button on the front.

I have tried task master and process explorer to try and find out what happens.

Basically an instance of svchost.exe hits 50% CPU usage (exactly and every time) and everyhting freezes.

The full description is

 

c:\windows\system32\svchost.exe -K netsvcs

 

I have found lots of instances on the net of similar problems where svchost hogs a large amount of the processor but never an instance of exactly 50%.

 

Any ideas ?