Its a new computer?
This is painfully simple....I know you said you turned off Avast.... but go in and make sure windows firewall is off.
Also go to "run" and type in "security essentials" open MSFT securiy essentials and make sure "real time protection" is unchecked.
I don't know how they ship it from the factory but wtf... take a look at both of them.
@Capablanca79 - I forgot to ask the obvious - have you contacted TOS support? did they have anything to say other than to reboot and to clear cache?
Try loading on another computer....I've got three you must have another....If you click on the "p" in "Updates" of the "Installing Updates" screen, you'll get a running log of what TOS is downloading, etc. This might help you isolate the problem.