Q: iTunes Update (9.0.3.x  to  9.1) Kills Microsoft Security Essentials!

I received a message that my iTunes app (9.0.3.x)I believe, was updateable to 9.1 when I launched iTunes this evening. So, I said [Yes} and it began downloading Quicktime and iTunes updates. When the download was finished the app asked if I wanted to install. To which I replies [Yes] when the install was complete I was prompted to restart my computer. [Sony RS-620G; Win: XP-SP3]When my computer rebooted I got a "Your computer firewall is not activated" [sic] message and my computer hung at about the second start-up app's loading. And there it stayed. Also, I noticed that I got a "Cledx.exe" error, and the "Task Bar" at the bottom of the screen would not respond unless I hit the "Windows" key!!
I booted into "Safe mode" and tried to run a scan with MS Security Essentials but the app would not load! I then deleted ALL APPLE Software from my computer.
And then tried to restart but my computer hung on at the same point at first then made it to the third loading app and then hung there. I then deleted MS Sec. Essentials; re-downloaded and installed. It's in the process of scanning and updating currently so I'll have to post again when it's done.
But, I'm just wondering if any one else has had the iTunes update to 9.1 WHACK their MS. Security Essentials app. The way it happened to keep MS.Sec.Ess from running was VERY VIRUS LIKE from my experience.
Any ideas, people?!!