Do you have an anti virus program scanning mail? Disable email scanning and see if that helps.

tashaman said

This latest update just installed has now caused my Thunderbird to ask me to enter my password for my email address which has never been asked for before and if I ask it to get mail I get the same request dialog box. I certainly do not remember putting a password for Thunderbird and the password used within Virgin I have used in the box I get the following message "Sending of username did not succeed. Mail server pop3.blueyonder.co.uk responded: Protocol error. Can anyone help and why with this update has it happened ? Ian Self

Thanks Matt yes I did and it now seems okay. Many thanks. Ian