I downloaded and installed the Avast Mobile Security beta with no problems and set it up fine after rebooting. It was after the 2 - 4 reboots that I kept getting a message to force close Avast due to errors, so I did. After this, I got messages to force close the phone due to errors and I had to pull the battery and uninstall the app. for the phone to work again and do a Master reboot, now all works well again.
I have an unrooted Samsung Infuse with no other security software on it. Previous AV was uninstalled and cleaned (like CCleaner), then rebooted prior to installing Avast.