KwikPhix,
You could try uninstalling PC Cillin and reinstalling it to see if that solves the problem.
Since you built the computer yourself, could you list all the hardware you used and a list of all your IRQs with every device on each IRQ so we could see what you are running.
Take Care,
Richard
P.S. The shovelware bundled with hardware is not full retail versions and are often buggy.