Can Not Send Mail In Thunderbird

Since installing BD internet security 2009 I have not been able to send email through Thunderbird (I do receive all my mail), but I can through Outlook Express. Somehow my SMTP port got set to 0. I reset it to 110 but that did not help. I get the message "an error has occured while sending mail. The mail server responded: Null byte in data. Please check the message and try again". If I try to resend the email I get the following: "The message could not be sent because connecting to SMTP server mail.bellsouth.net failed. The server may be unavailable or is refusing SMTP connections. Please verify that your SMTP server setting is correct." I did all that and I contacted bellsouth and verified my settings and that everything on their end was working. I also wrote the Thunderbird forum and they seem to think it has to to do with BD.


Any ideas???


Thanks.