I had the same problem with my male veiled. He would get very dark and wander constantly around the bottom of his cage looking like he was searching for something. I put towels in the bottom of the cage to protect him when he fell in his rush to get to the bottom. Well, he started digging frantically in the towels as thought he was trying to get away from something and I was at a total loss. Anson, one of the regs in here, told me to clean the cage out thoroughly and change the plant arrangement around a bit because there may be something in the cage that the cham didn't like. I did this,and like magic, the cham was fine again. Hope this helps.
Marilyn