Hello 1dc and welcome to the forum.
1. What version of Avast did you install? 5.0.677?
2. What other security software do you
currently have or did you have
in the past on this machine including antivirus (AV), firewall, and other security programs? If they were in the past, how did you remove them (the vendor's uninstaller's tool or another way)?
To let you know, there have been other users on the forum that have reported conflicts using Ashampoo FW and Avast. Once this FW was uninstalled Avast worked properly. If you want to
try it with your FW, make sure Avast is not being blocked by the FW, but it is strongly recommended that you uninstall it and replace it with a different FW.
Update parameters I only connect to the internet using a dial up modem.
Proxy settings Direct connection (no proxy)
Change your Settings > Update Parameters > click "I only connect using dial-up modem" > Proxy settings...enter the information needed.
Let us know how this works. Thank you.