In reply to RichG:
This is not an uncommon occurrence, some kids bounce back pretty quickly and others take longer. what you choose to do is going to be limited by whether this kid comes in a group or on an individual session.
I think the most important thing is to work out whether this child wants to continue coming along and climbing and whether he still enjoys it. If he wants to keep climbing and is fine going a little way up but not achieving the top of the wall then is there really a problem, lower him when he's ready and don't make a big issue out of it.
If he's getting disheartened or upset about not getting to the top then a very simple sticker style-reward chart may prove helpful.
No matter what you go with don't underestimate the value of asking simple questions of him about why he gets scared, he's probably aware of it even if he tells you he doesnt know, and involve the parents, talk with them too if you get the chance.
Post edited at 18:06