Save your old file as url.old and create a new file in notepad with this:
[SERVER_NAME]
1=free.grisoft.cz
2=ftp.grisoft.com
3=www.grisoft.com
[SERVER_URL]
1=http://free.grisoft.cz/softw/60/fe
2=ftp.grisoft.com/pub/softw/60/fe/
3=http://www.grisoft.com/softw/60/fe/
Actual URL=3
When you restart AVG you'll have three choices to download from instead of the default one.