Re-application
Guys, the answer to this question is buried somewhere in this thread (I'm not going to do the arrogant "if you can't be bothered to find it etc etc" speech) - have a look, it's all there.
However, just to re-cap:
Your second ATTEMPT at the ASSESSMENT DAY has to be AT LEAST 12 months from the previous one.
You CAN apply prior to 12 months, but no sooner than 11 months from your last APPLICATION. So if you did selection on 22 May 07, you can't do it again sooner than 22 May 08: they will check this. Depending on when you applied for the May 07 attempt dictates when you can re-apply. So if you applied in Feb 07, you could apply for another go in Jan 08...but wait until 22 May before attending!
Be careful, it locked me out the 2nd time too, phone call to Recruitment sorted it though (very helpful/efficient but extremely busy also). When you phone them, you will speak to an operator who probably won't be able to sort it there and then, but will refer the case to the actual Recruitment guys. The problem is your application gets 'screened' and they use the Day 1 date of last year as the start of the 11 month period, even though it's not quite correct, and you might find it gets automatically 'binned' - but you do get an email saying it's been binned for that reason: this leaves you having to phone them to get it fixed, but as I said it's not a major problem.
To make it completely hassle-free, you could just wait until 22 Apr 08 (using the above example) before re-applying, but you may just have to wait beyond May before getting a date.
Hope this clears up the confusion, and is useful to those applying. Good luck.