Slowed performance since latest update(jan. 6th 2011)

My CPU usage spikes constantly from the under 10% range to over 70%

This has just started since the most recent update. I have ran a full system scan and there have been no security threats. I run live update multiple times a day with smart definitions off.

I still have 80GB free on my hard drive

My laptop was never slow before.

 

Windows Vista 64 bit Home Premium

Core 2 Duo

4GB RAM

500GB HDD