I signed up 8 times to fly 109G with some squaddies. Still does not show me on roster.
First time it showed the position filled after I signed on. Later Soulyss said I did not appear on roster. Went back and it still showed an opening.
Seven more times I tried...... there is a problem. 
I know. I'm trying my best to get it fixed, and have been trying for a while now. It is very frustrating, I know.
In the meantime, please check ahevents.org to make sure your forum name and message-board ID is correct. (Go to "User Menu"->"My AH Events Profile" and make sure that what you list for "HTC's Forum ID", etc., is correct, and if not, update it.) Almost all forum problems are a result of registrants not putting in correct forum ID's.