You usually do fine with transparency with all printers if you flatten it at high quality. If you make a pdf compatible with Acorbat 4 and select high quality in the transparency flattening section of teh pdf export options, it'll usually be ok.
The problem seems to be that some printers, and/or their equipment, can't, or don't know how to, handle unflattened.
Using OSX 10.3.9 on a G4