Windows Live mail error message

[#1]

Hi All,
The last two days, when trying to Send/Receive messages with Live Mail I have had an Error Message pop-up window showing the following message relating to three of my addresses:
"Unable to send or receive messages for the Hay__[part deleted for security]____lk.plus (john) account. Your server has unexpectedly terminated the connection. Possible causes for this include server problems, network problems, or a long period of inactivity.
Server Response: +OK 35236 octets follow.
Server: 'mail.plus.net'
Windows Live Mail Error ID: 0x800CCC0F
Protocol: POP3
Port: 110
Secure(SSL): No"
This message repeats three times for different addresses (probably my most used ones), but not for all of my addresses.
Please can anyone throw light on this?

[#2]

0x800CCC0F usually means a time out attempting to contact the server has occurred.
Closing down your mail Outlook and reopening can commonly help with that, otherwise you might want to check your firewall and antivirus settings

[#3]

Thanks Adam,
Disabling antivirus (Avast!) enabled me to receive emails once again, but I could not see a faulty setting.
Strangely the a/v software hung during a program update on Saturday, and I could not get it to restart.  I have now manually installed the new version from the website, and all appears well.
Thanks again for looking at this,
Regards, John