I'm sure this really doesn't help, but I have been unsuccessful in using a Rio Receiver or Audiotron with an Orinoco EC. Sometimes it would work, then it would not work. It really bugged me... a lot. In fact it bugged me enough to put my wireless router/switch and music server in my stereo cabinet.

I tried getting it working for months alternating between the Rio being wireless and the server being wireless. Each setup caused the same problem you have after an short period of working. I then realized that if I reset the router (SMC Barricade), the problem would be fixed.... for a short period of time. I am reasonably sure that the problem was with the SMC router. If you have an SMC, that would only serve to prove my theory. I have been able to "crash" this SMC router on other occasions as well with large file transfers.