Is there any way you can put some Damp-Rid in your cryostat chamber or in the lab?  You can get the stuff at any walmart, hardware, etc...type store.  Better yet, buy the active ingredient as a chemical and it should be cheaper.  A much more expensive alternative, just in case the new a/c doesn't fix the problem... buy a dehumidifier for the lab.
Good luck, 
Sylvia Poulos
USDA-ARS-Animal Physiology Research Unit
Athens, GA