Another one! Yep, happened to me when my ISP's mailserver went down. TRF tried to send me mails which bounced and I ended up with the same message.
Either that or you've been banned.
Once the ISP's server was back up, I changed the email address of my username to another email I have. Once that was accepted I changed it back to the original email. Long workaround, but TRF wouldn't let me just re-authorise the same email address.
You have my attention. @mo2872 If the thread was contentious and getting off topic a lot, it could be the thread. Also, if someone is having to have posts deleted in a thread often, mods can ban a member from replying to a thread. Have you had any posts deleted on a thread by being less than a polite gentleman?
If you would like to PM (Private Conversation) me what thread you cannot post on now, that you have posted on before, I'll be happy to check and see if I can find the issue for you.