Cathy, I may be wrong but IMHO the only way to save it it's to cut all rotten parts, disinfect it, treat with anti fungal and keep it dry until it calluses over, then pot it in to a dry mix and wait with only misting. I guess, you pruned roots and repotted right after, so there were not healed exposed cuts covered with soil and all bacteria and fungal spores could get in. There are experienced DR growers here who will most likely give you advice soon.
Good luck, Aggie

I do the same thing that Aggie suggested. I take a sharp clean knife (wash it with bleach) and cut out all the rotted tissue then dust it with a fungicide and allow it to dry completely. As long as there's enough healthy tissue remaining and the rot doesn't spread this usually works well. Good luck.

Thanks everyone, I guess I'll gather up my wits and dissect my poor plant, can't see what else I can do wrong. I've plucked off all the buds hoping the plant can put all it's energy into healing. Fingers crossed!

if you look on you tube when they cut the roots they leave them out to dry for some time...i would research it!