treating / preventing bulb rot

[ttinwa]

I lost several orchids (maybe 15?) recently - about half of my collection. In almost all cases, they ended up getting some sort of rot (in the roots and or pseudobulbs), which kept coming back despite aggressively cutting away diseased parts and sprayed with diluted Physan. After I treated them, I experimented with spag-n-bagging, putting some of them in moss, some in bark, and some in S/H, but have yet to save one of them.

So I have two questions:
1. What conditions could be causing this? My guess was inadequate air flow and/or too high moisture with no drying out, but maybe I have some sort of pathogen?
2. Is there any effective way to treat rot once it happens? I have a few plants clinging to life at this point, but what I'm more worried about are the plants that I still have - could be the difference between an expensive lesson and just quitting the hobby altogether.

- Tom