Hello all,
This is my first post and I am an orchid newb, so please forgive if I'm asking a silly question.
I bought my 3rd orchid, a zygopetalum of mature size from Orchids.com, and it has seemed to be healthy and happy (though spikeless) for the past couple of months. (URL of the scientific name and pic here:
ORCHIDS.COM : SHOP : BOTANICAL : DETAIL)
However, I went away for the weekend and its leaves have begun to yellow (sometimes from the tip, sometimes from the base), turn brown, and fall off. There are four mature pseudobulbs and a couple of new growths, and the whole plant looks really green and healthy. I tried repotting, and discovered that about half of the roots are starting to turn a bit brownish and a little slimy, so I'm guessing that I have a root rot problem.
It is potted in a medium bark mix and gets plenty of indirect light and no standing water, so I'm wondering if it started rotting before I received it. I'm going to do some surgery tonight and see if I can't save what I hope will be my favorite orchid, but I wanted to get some feedback from the more educated masses on whether or not I should buy from them again.
Does anyone know if Orchids.com is reputable or not? If not, are there any better online sites I may patronize to continue my fledgling collection? I also am having a problem with a phael/dendrobium hybrid that I bought form the local Safeway, but I'll save that for another post.

However, I also have a very healthy Phael (my first orchid) and a young Vanilla Planifolia that is extremely happy winding its way around my bathroom window, so I'm not a *total* inept loser at these gorgeous plants.
Help me find a reputable outlet for my burgeoning obsession, please! Oh, and thank you all for the knowledge that I have gleaned thus far by simply lurking and reading!
-Jen