Over what period of time did the plant lose its leaves? There are a couple of common senarios here.
When a phal loses its roots then the leaves tend to wrinkle, go yellow and fall off over a period of several weeks.

If you plants lose theirs over a few days then it is more likly that they are suffering from crown rot where an infection gets into the plant and it goes downhill quickly. Crown rot is often caused by water getting into the crown of the plant by misting or watering.

Plants with few roots are best under watered and kept warm until new roots can develop. In bark, in a warm room, after repotting I would water every 10 days or so. If the plant has no roots then water less often.

What kind of light are the orchids getting?

The two that had no roots alive when I re-potted them (one of which is already dead) have been losing their leaves over the last four months or so (about 5 months ago I re-potted them). The other one (that had roots that now look completely dead), has not lost any leaves yet, but it is now completely loose in its pot due to no good roots (I assume). They are all in unshielded north windows - it is the only place in the house that I have been successful with my orchids (w/o artificial lights).
It also sounds like I have been over-watering them. At home I normally need to water my orchids once per week, and I have been watering these twice per week, as I thought maybe that would stimulate new roots (not sure where I got that idea from and clearly it has not been working)...

On a side note - how do I post pictures - I have taken pics that I would like to share.

Thanks for all the help!

Know the feeling, repotted about 20 of mine from bark to a mixture of bark and diatomite, thought it would reduce chances of root rot. lost about half of the repots in the first year

What's the best way to water bark versus moss? I usually soak mine in bark for 10 minutes, about once a week. When I bought an orchid in moss, it didn't try out and started looking shrivelly...

You haven't said what part of the country your in. In most cases northern light is very weak light, the weakest of all four directions, and the plants would get very little stimulation to use much water. Watering twice a week is just the opposite of what plants in northern light need. Their watering needs would probably be stretched to ten days or even longer. Any more frequent could rot the roots.

I live in OK (stated in my original post) - My orchids at work gets watered twice a week and have excellent roots (warmer there than at home). The ones at home gets watered once per week - except for these that I was trying to stimulate new roots in - I watered this two times a week, which was apparently not the right thing to do. All of them are in north windows, nothing shielding the light.
Thanks for everyone's help!

Sounds like over-watering. They sound pretty distressed. Is there anyway you can raise temps to 80*? If not, bring them to work to recuperate. Phals can take pretty cold temps but when they're stressed, warmer temps will go a long way in bringing them back to health.

I give my phals a lot of light. I'm in zone 6 (NYC) and they are on SE or SW windows (no shading, no obstructions) during the winter. If your other phals are doing fine on the northern window without any additional lighting then don't fix what isn't broke, but if you wanted to tinker and see more spikes and faster growth, try adding some CFL lighting.

AS for posting pics, you need to upload your digi pics onto some website like picasa, flickr, or webshots. Then follow the instructions on the website for sharing your pictures. Usually it's just copying and posting the html code of your picture onto the gardenweb forum message box.

Hope this helps and remember to post back with updates on your phals.

Steph

Ok, so a higher temp is better when distressed? Then I should bring them to work (although it may be too late). The reason for the low temps at home is my chinchillas (they require low temperatures to be comfortable). At work I have my own thermostat in the office so I keep it warm during the day (80 or so) and then I turn it down when I leave (probably 70 or so). That seems to work extremely well and then form new spikes almost immediately after the old one goes away - it is a blooming factory since almost two years now. At home they will re-bloom, but not as quickly. And what you are saying makes sense, because the only place I have to buy orchids in this small town is when they have them at WalMart and most of the time, you can't even check the condition of the roots - and the ones that have so and so roots to start with immediately grow nice root systems at work, but the ones at home take much longer.
Thank you so much for your help! I really appreciate it.

I feel your pain, I don't have a greenhouse so I grow my cool growing orchids right next to my warm growers on the windowsill. Neither are happy but atleast they're not dead.

Good luck with your phals and keep us posted.

Steph

Hi, I have about thirty plals and i believe have had the same problem as yours. When i repotted certain plants, usually larger phals i have had some problems, i believe in my case the plants were under watered. Everything you read on repotting states that you shouldn't water for at least ten days but i think my problems were caused by not watering enough. I have many miniature phals. in clay pots and bark or coco chips and i water every other day. I grow under lights in the winter and my watering schedule seems to work well since the plants are thriving and blooming, good luck Hank......

Sorry about not catching that you're in Oklahoma. You're growing in two different climates, at work and at home. You might try the skewer method of watering. Get some shishkabob skewers from the grocery store, trim them down and put them into the medium halfway between the plant and the rim of the pots. When you think a plant needs water, take out the skewer and touch it to your lip, cheek, or the back of your hand. If the skewer is wet or damp, don't water. If it's barely damp or dry, water. How wet or dry the skewer is before the plant needs water will depend on what type of plant it is. Phals don't like to dry out but cattleyas do.

Thanks - the skewer method may be very good for me to use at home where it is cooler and more difficult for me to grow the really nice and healthy roots. I had read about the 'pencil' method poreviously but was concerned that I would damage roots sticking it in the pot, but a skewer is smaller so that may work better.

Thanks for all your help!