clpfd constraints not taking effect

Hi,

I have a whole bunch of constraints being fed into clpfd, however
sometimes some of them don't seem to take effect. I've reduced one
particular case down to something like this:

?- B #= C+1, B #< D, C #>= 10, C #>= 100.
B in 101..sup,
B#=<D+ -1,
C+1#=B,
D in 12..sup,
C in 100..sup.

The last constraint doesn't seem to have taken effect
B in 101..sup, but B < D, so D should be reduced to 102..sup.

It works as I expected if I:
* swap the last two constraints around
* or remove the C#>= 10
* or add another constraint C #< 1000000

Any ideas what's happening here, and whether there's anything I can do
to force clpfd to enforce all the constrains without having to try and
enforce an order on the constraints or add arbitrary constraints to
avoid sup?

Thanks
-- 
James Hogan