shutterbug

Try to cut down on the time of his daytime sleep, but not too much, otherwise he'll be more fuzzy at night.  Maybe he's sleeping too much and too well during the day so he doesn't want to sleep at night.  Make him feel as comfy as he can during the night and maybe try to leave a lamp on or have some dim light.  Sometimes very light music in the background might help.

Anyway, you pretty much have to try all the combos to see which method works.  There's no silver bullet!