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.

After a search on the Avast forum, I came across this post, claiming there's a problem with certain applications and Avast on XP:

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This is caused by a bug in Windows XP function ImageEnumerateCertificates( ) which is being called by firewall service when a process tries to access the net. This function (unpatched in all version of XP) hangs with certain corrupted files and LogitechDesktopManager.exe is one of them.

It will be fixed in the next program update! Until then, either uninstall LogitechDesktopManager, call them to have their file fixed or update Windows.

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.