WN3000RP - very slow wifi speed

[svos]

Hi.
Just get the WN3000RP connected in my house.
No problem to connect it to my Netgear WNR3500L router. The wifi-range is now very much higher
But the speed is very slow. When I connect my laptop to the WN3000RP, I only get about 400 Kb/s. When I connect the laptop direct to the WNR3500L router, I get about 13 Mb/s.
Also upgraded the firmware to v1.0.1.18, and try enable the mac-address access control.
Any solution?

regards
svos