Devices used:
- RB2011UiAS-2HnD-IN, RouterOS to v6.29.1.
- Toshiba Satellite U500-1F4 with Atheros AR9285 wireless adapter.
- Other Wi-Fi devices, such as Galaxy SII phone and Toshiba Satellite A300-20Q (all N-capable).

There is one wireless network configured with hidden SSID.
Wireless connection in Windows 7 has been created manually with WPA2-AES-PSK and options to connect automatically even if the network isn't broadcasting SSID.

If the network is "2GHz-only-N" U500-1F4 does not connect. All other Wi-Fi devices connect flawlessly.
If SSID hiding is off or if network type is "2GHz-B/G/N" or "2GHz-only-G" U500-1F4 connects automatically.

How to determine on which side is the bug and how to eliminate it?