You have to understand that some people DO come here and do exactly what you described in your message. You didn't say anything about reading up first or what kind of light you are using. We get all kinds here and it is often very frustrating to help people with limited information. I would have liked to have seen what kind of light and what kind of enclosure and if you were feeding anything in addition to crickets as well as the expected age of the crested.
My guess is he might just not be used to this new, big, shiny world that looks nothing like where he used to live. Also he could be startled by the sudden light, your other gecko is probably used to you doing this month after month. Make sure you are offering Crested Gecko Diet or one of the other MRP in addition to crickets if s/he is a young one, that is how I find they grow the best.
Cresteds have VERY different personalities, mine probably has ADD in fact, but I will say after a year or a year and a half she settled down a little bit. My brother in law's gecko is so out of it I think it hit his head too many times... oh course, that is the gecko I THOUGHT I was getting when I got little miss ADD. But I love her... when I can catch her. 
Good luck.
-----
0.1 Albino Leo Gecko
0.1 Crested Gecko
1.0 Dear Boyfriend
Departed: Harvey and Spock