Boot Troubles

Just a quick ? After installing and playing around with CPF which I find to be an excellent product, so much so I downloaded and installed the Antivirus as well :). However I have noticed that if I install additional programs or in my case with a new computer I have been using Windows update, when I reboot a number of times I have had my computer lock up so that I have had to cold boot it to get it to restart. Is anyone else having similar problems or can anyone offer any help. I’m running xp home sp2 and the last CFW installed today! Thanks in advance.