Hi!
I got the same problem.
I use DIR-615 router (firmware 4.0)and a DWA-131 adapter (driver 1.2), Windows 7 (x86)
I got 80% of signal.
Settings: only WPA2, AES and 20/40, Auto.
The RX sign in the D-link Manager jumps between 40-120 Mbps.
You got the solution?
Thx!