Well, did the reboot as requested, and sure enough, not a single one of my programs worked. Thankfully I set a restore point before the Avast 5 install, and through rebooting into safe mode, I was able to get my computer back - exact same thing as last night. Yes, I am completely frustrated and befuddled that it should be so hard to upgrade to your latest version. I never had any problems with version 4. I followed SafeSurf's instructions exactly, using the removal tool twice in safe mode (rebooting in between), etc. All other programs were closed.
As I mentioned in my original post, I have Windows XP Home SP 3. I also have Spybot and Super AntiSpyware installed. However, neither one of these programs run constantly. I only use them to do spyware scans. I have Windows Firewall.