Help with email problems?

I have several email accounts within Outlook. It seems each day, one of them goes awry and I get the following error:

"The POP server responded with an error: (Account: Sales, POP3 server, mail.domain.com, Error # 0x800ccc90 and 0x800xxx0e)"

Upon a search with my hosting provider, I found that this can be caused by Norton or some anti-virus software interfering with the connection, or even a firewall. I dont have a firewall and when I got my new computer, I used a "de-crapifier" program to get rid of all the Norton, McAfee, etc. junk programs that were on here. I'm wondering if something was left behind that my email is not liking? I do use AVG, however I used it previously with no problems and I do need to use it to scan for viruses in my email.

Does anyone know what still may be causing this? Is there anyway to determine if there are some small, hidden files that Norton may have left behind that would be interefering? (I did a search on my computer for "norton" and I used hijack this with no success) Could AVG be causing this error and what can I do about it if I still need to use it?

The strange thing is, if I go in and delete the problematic account from Outlook and put it in again, it works fine for a while until I restart the computer. Then it seems to pick another email account to mess with the next day! Really frustrating.

Thanks for any help!