Check the account properties advanced tab. Have a look at which ports are being used to connect to the mail server (from the error message it appears that port 10061 has been specified). Pop usually uses port 110 and smtp port 25 (click on use default ports). Looks like they are using different port numbers from the default (both the same looks fishy too).
Is there some anti-spam software running? Not familiar with Norton so I can't say whether it has caused the changes.