Long shot - in an earlier post, you said transformer secondaries - are you using a transformer with multiple secondary windings that can be connected in series to double the output voltage, or in parallel to double the current capacity? If so, and you're doing parallel for additional current capacity, are you sure that the windings are phased correctly? If you wire them in opposition rather than in phase, they're effectively shorted, and you'll get no voltage out and a very hot transformer.
If you have a dual secondary transformer and you're doing the parallel thing, try powering the supply with just one of the secondary windings and see what happens.
-Pat