URGENT Online Forms

i fill up my examination form online...i get to the confirmation page..i confirm..and when i get to the transaction page it states transaction invalid..for what?..is there a specific time of the day when one is supposed to be filling these examination forms...if there is then that would explain this message...the worst part is after ive filled in all the dtails..i go to the transaction page ..and it stalls me..i try to go back..to examination detalis page and i cant..so i log out and log in again..and then all my details are gone..i have to start from scratch all over again..if anyone could possibly just tell me whether there is a specific time i have to be filling up these exam forms