I have WAP11s in Client/AP mode working. I had similar porblems to you at first. I even put a sniffer on the other side to see if packets were making it across. The odd thing is some were, but not all.

The solution turned out to be the switch I had the Rio on. I have the Rio going to a switch along with the WAP11 client. When I changed that to a cheap hub everything worked. Very odd since SOME packets did make it across the wireless link when using a switch.