Hello,
thank you for your detailed explanation - makes it easier for me to help you.
although there is still one question left: you reinstalled Anti-Theft, right? did you choose rooted installation in the setup process?
in my next explanations, I'll assume you have Mobile Security installed with active uninstall protection and Anti-Theft installed rooted.
the first thing you'll want to do is to uninstall avast! Mobile Security AND Anti-Theft to reset your avast! PIN.
to remove root installations of Anti-Theft, use the free tool "Titanium Backup".
alternatively we offer a uninstall.zip at
http://dl.dropbox.com/u/27553331/root%20uninstall.zipunzip it and run uninstall.bat with your phone connected via USB to the pc. make sure usb-debugging is enabeled on your phone and the phone driver is installed on the PC.
If you do it on the PC where you rooted your phone you usually have these drivers available.
hope this helps!
if not - contact me again and let me know what you tried/where you failed.
Werner