I've noticed that since I installed the monthly Windows XP Updates on Tue 14 June 2011, my PC is temporarily unresponsive on start-up, say for a minute or two. Afterwards, the problem goes away (until the next reboot). For example, if I double-click the Firefox icon just after start-up it takes around 45 seconds before the main Firefox window appears! If I try it a few minutes later though, it opens in just a second or two.
I remember I had this problem before and I put it down to the .NET Framework assembly process after installing Windows Updates. However, that issue resolved itself after a few days. This time the issue is still persisting after over a week.
I'm using XP Home, with SP 3. As a precaution, I have done a virus/spyware scan and all is reported clear.
Any ideas what is likely to be causing this and how to resolve?