If you can connect to G but not N, check your SystemInfo=>Network=>WiFi settings, and see if your country code is Taiwan. That appears to be my problem. Now trying to figure out why.
Interfaces:
en0:
Card Type: AirPort Extreme (0x14E4, 0xD1)
Firmware Version: Broadcom BCM43xx 1.0 (5.100.98.75.6)
MAC Address: 58:55:ca:f7:36:23
Locale: FCC
Country Code: TW
Supported PHY Modes: 802.11 a/b/g/n
Supported Channels: 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 56, 60, 64, 100, 104, 108, 112, 116, 120, 124, 128, 132, 136, 140, 149, 153, 157, 161, 165
Wake On Wireless: Supported
AirDrop: Supported
Status: Connected
Current Network Information:
ronopolis:
PHY Mode: 802.11g
BSSID: e0:91:f5:05:1d:7e
Channel: 6
Country Code: TW
Network Type: Infrastructure
Security: WPA2 Personal
Signal / Noise: -47 dBm / -90 dBm
Transmit Rate: 54