Any hints on installing a Hampton Bay ceiling fan on a cathedral ceiling so that it will not 'wobble' out of balance?

Did you instal it with the blades at the same slope as the ceiling? If so, you may need to check HD for a longer rod and instal it flat.

Besides having the fan mounted so that the blades are level horizontally there should also be balancing weights that are attached to the blades to correct wobble.

All the blades properly tightened? Where on the ceiling is the fan, sloped side or peak?

Hee are excellent instructions on how to balance a ceiling fan:

http://www.ceiling-fans-n-more.com/blade-balancing-issues.php