Syed,
If you haven't, I would advise you to start by contacting Oracle. Years ago I had something similar. I was trying an RMAN recovery (fortunately test). A network-attached drive was involved. Oracle said: "well, take that drive out of the picture." I tried that and it worked. Then I went back to the network guy with proof. Turned out that even if you open a single channel in RMAN it opens several paths through the network.
Good luck Dennis Williams