After updating to an SSD I also updated my virus scanner to the latest version of Trend Micro Titanium. I have noticed less activity after my computer loads Windows than before though I did have a period last night where I would get a busy signal, if you like, when I hovered the mouse cursor over my Task Bar.
Maybe I need it not to do regular scans on the system but keep the real time checking of Internet and email downloads, which should be enough. My computer is only on for as long as I need it to be.