@ pbxl
I believe what Igor means is for you to try a reinstall (uninstall, reboot, install, boot.) in the default folder, don't use a special directory.
@ mitchemjack
If you can answer Igor's questions and if in a different folder to the default try an uninstall, reboot and install in the default folder I assume you are using the English language version ?
If already in the default folder a reinstall might resolve it if the install was bad.
I have my English language version of avast in a different partition but the same general path, D:\Program Files\Alwil Software\Avast4 without any problems.