Bug resampling field with Irregular2DSet to Linear2DSet

I'm trying to resample a field for which the domain is an x/y tuple defined
by an Irregular2DSet, and the range is a simple RealType.  Basically I want
to make an interpolated image out of a scatter plot, so I'm resampling my
field using the points of a Linear2DSet.

Any simple examples I create seem to work fine, so I'm unable to give a code
example that demonstrates the problem, but my symptom is that large portions
of my resampled field are filled with NaN.  If I offset my x values so they
are all positive, then missing horizontal strips are resampled properly.  If
I offset my y values so they are all positive, then the missing top
portion(which is sometimes everything) of the data gets displayed properly.

I find the resampling code pretty intimidating, but I'm hoping a developer
can look through it and pick out the problem.  If not, then I'll have to
send my whole set of data(2900 points), or the Irregular2DSet created by
them.  I'm pretty sure the triangulation is OK, because a plot of the field
whose domain is the irregular set itself looks reasonable, and I can easily
evaluate the field for any pair of coordinates OK.

I've even tried to create an equally complex irregular set from random
points, and I still can't recreate the problem except with my specific set
of points.

Anyway, I put some quick screen-dumps illustrating the problems at
http://gritstone.ca/personal/igraham/VisADProblems/VisADResamplingProblem.ht
ml

Thanks for any help resolving this!

Ian