Can't connect to Internet from router when using AP

[EarlofSandwich]

Hi, I have two RT-N56U with different names configured using Padavan's firmware.

Router using WPA2-Personal, Wireless Router Mode

• Bridge is set to AP Only mode
• IP Address 192.168.1.1, Subnet 255.255.255.0
• SSID ASUS (2.4ghz) on Channel 6
• SSID ASUS_5G (5ghz) on Channel 36

AP using WPA2-Personal, Access Point Mode

• Bridge is set to AP & AP-Client modes with the Router's 2.4Ghz and 5Ghz SSIDs registered using WPA2-Personal
• Static IP Address 192.168.1.9 (excluded from DHCP pool on router), Subnet 255.255.255.0, Gateway 192.168.1.1
• SSID ASUS_B(2.4ghz) on Channel 6
• SSID ASUS_5G_B (5ghz) on Channel 36

Recently I haven't been able to connect to the Internet for PCs connected to the Router when the AP is turned on. Access to the Internet for clients using the AP is fine so the two RT-N56U can communicate to each other.

When the AP is powered off, PCs connecting to the Router can again access the Internet. The same issue happens when the two RT-N56U boxes are swapped using the identical settings, or even when the Router uses the ASUS stock firmware. I have tried both wired and wireless connections between the RT-N56U boxes. For testing purposes they are sitting almost next to each other to limit interference.

1. I was previously able to connect to any SSID and access the Internet. What might be affecting it now?
2. The AP is used for wireless and wired systems (e.g. WDTV and a tablet), how could I use the SSIDs and channels to best maximize my throughput?

Thanks.