[Lost Leader]

I think this happens when after you have filled in your name and pass-word to log back in a box comes up which says something like thank-you for logging in and there is a button marked "proceed". What you must not do is click on that button. If you simply wait the box and button will simply disappear and another box will appear saying thank-you for posting and all will be well.

Don't know why it happens in the first place though - it seems to depend on the length of the post or the time you take to write it.