My Avast Does not want to update neither automatically or manually
How long has this been occurring (or rather, not occurring), what firewall do you use, what operating system, how long has Avast been installed, and was anything else installed prior?
oh, tarq57 was faster than me… 
how are you connected to the internet? (dial up,…)
Please, post the last 200-250 lines of avast log: C:\Program Files\Alwil Software\Avast4\DATA\log\Setup.log