Unstable internet connection

OK here's the situation,My friend has Windows XP,recently her Nortons Internet Security 2005 subscription was running out.she decided she wanted to change her protection.She heard about Avast antispyware and decided to go with it.First she had to unistall the Nortons which she did.Then she Downed the Avast program and filled out the registration for it.When she went to sent it however she lost her connection.She has the program installed, she just does not have the key to finish.Now everytime she connects,she is on for about ten minutes or so and gets Booted off.After some looking around we discovered that under her internet properties,in the settings field,there is nothing listed in the username in Dial up settings.Could have Uninstalling Nortons somehow changed her settings.We went to control panel,Internet options,connections,settings.and her Automaticaly detect settings was unchecked.Can anyone please help me to help her.She can't maintain a connetion to do this by herself.Would re-installation of her ISP resolve this?Any help would be greatly appreciated.She looked in her isp log file, because she is constantly loosing her internet connection, and found these 2 things listed AB Sync error:100 + invalid cn:1. what are they?She can not connect so im trying to help her out.