This is a distinct possibility.  First rule out any medical problems, as has
been suggested.  Also, there is a much higher incidence of behavioral
problems in declawed cats than in clawed cats.  In addition, they often
develop arthritis -- earlier and in a more severe form.  If this is a
possibility, try to find the very softest litter you can locate.  It may be
that your cat feels pain when he tries to dig in the litter.  If that does
not appear to be the problem, you might want to try Cat Attract litter.  I
don't have any experience with it, but it has helped with my sister's cat (a
cat that is declawed and exhibits many of the behavioral problems common to
declawed cats, including spraying and urinating outside the box).

MaryL