Alvaldo,
This is symtomatic of a shortage of available memory.
Rebooting will regain lost memory automatically.
What exactly do you mean by the Download Shutdown box?
Are you referring to the "download" progress box?
If Windows is freezing prior to completion of the download, then more than likely, the Avast setup file is corrupt or incomplete.
You said that when you reboot, everything is ok.
Does this mean that Avast works properly?
