Unexpected behaviour using CAS solve (Fixed)

[StephenG1CMZ]

Whilst implementing a distance-to-horizon program, I saw some unexpected behaviour using CAS solve. On the 1st run results seem OK, but on subsequent runs all solves return undef, suggesting an initialisation issue.
http://www.hpmuseum.org/forum/thread-12769.html
One possible problem is that the cas solve is using upper case home variables, not cas variables...
But except for the one Print cas solve, other solutions are as expected.

Update: Changing the solve to solve for h instead of HT seems to fix the problem.