I also had a problem where I couldn't post. Whenever I logged in, the only page I could access was my p-mail and the account settings page. This occured on Firefox and IE on XP, and IBrowse on WinUAE. I got tired and made a new account, and then it all worked.
If you want to play around with my account which won't work, log in as "askripel" with pw "hahaha".