Dying Paphiopedilum

[paphlovian]

I have just assumed there is nothing I can do to save my first dying orchid. It is a paphiopedlium that a friend gave to me after it was finished blooming. It has both the old growth which the flower spike was cut from and the new growth. Just during the past week or two, the entire plant has started yellowing and will not come out of its droop. I had repotted it several months ago, at which time I used a fine bark medium, along with a little bit of spaghnum moss at the roots. When I repotted it, I noticed that the much of the roots had rotted off, leaving one black root. The plant has been looking okay (not wonderful) until the past week or so. I just assumed it's a gonner, but thought I'd attempt to save it if someone has any ideas. Also, if I do loose it, I'd like to know just what I could have done to avoid its death, for future reference. Thanks for all your help!