Edgar digs in his litter too.  But usually only when its new.  I was using
Johnny Cat, but he seemed to use that less and less.  I guess he hated the
moisture activated perfume or something.  Then I tried EverClean heavy duty
clumping litter.  After I finally got all of the *cement* off of his face
and fur, I am now trying Cat Country natural pellet litter.  He started
doing the backstroke in it even though it was kinda dirty at one end,
meaning that maybe the oder control in this stuff works *too* well.
Anyhow, 'bout that time (yesterday) I took him into the vet for #3 canine
distemper and rabies vaccines--never any reaction.  Vet pointed out that he
was cryptorchid (only one testicle descended) and that this may be the
cause of his erratic preeing and such.  He also mentioned that cryptorchids
have been known to behave *very* strangely, and that it was best to go
ahead and neuter him, which I had planned to do anyway.  I had figured that
the other would drop when it was good and ready, but apparently it might
never have.  So, now he's back, minus some fur and flesh, and is 3 for 3 in
the litter box--yeah!  I'll wait to see how he is when he gets his energy
and strenth back...wish me luck.....Nevermind, now he's playing in
it...(insert passage of time here) ah, now I see....everytime he starts to
actually dig, grab out and smack him on the head.  Wait until he actually
starts to dig, so he doesn't think he's being punished for being in the
litter box.  I just hover over him as he's got his front paws in the litter
and wait for him to dig, when he does, pow!  Negative Reinforcement.  Seems
to be working great.
[Posted in FML issue 1303]