[idvusers] Error when trying to load from catalog

I got this error when trying to load from a catalog:

        Error: Could not load url: 

I can reach http://motherlode.ucar.edu/thredds/ with my browser but don't 
find an idv directory there.

James F. Drake
Mission Data Exploitation
Meteorological Satellite Systems
HQ Air Force Weather Agency / The Aerospace Corporation
101 Nelson Dr.
Offutt AFB, NE 68113-1023

Phone: 402-292-1274
Fax:      402-291-3137