Had a problem with an XP (SP2) computer and Avast Internet Security. Upon installing the product (and its subsequent reboot), the computer freezes right after startup. The mouse still moves, but keyboard does not respond, no applications get started.
While the computer was not running Logitech Desktop Manager (as mentioned), I did select not to install the Avast Firewall. Another post mentioned to disable the behaviour shield which I did as well.
I uninstalled AIS and reinstalled it without firewall and the behaviour shield and look: no more problems.