iMac AirPort Extreme Card is picky about specific channel

Hi,
I have a 24" iMac and it has
Card Type: AirPort Extreme
Firmware Version: Broadcom BCM43xx 1.0 (5.10.91.27)

I just bought a Motorola SBG6580 Cable Modem that has Modem, Wireless router, and Ethernet router in one.

I've tried to broadcast the Wifi using Channel 1-11, but it seems that the AirPort Extreme only like to be on Channel 1. e.g. I would get no signal or extremely low (not useable) signal when in channel 2-11.

The odd thing is that Channel 1 has the most interference in my area. This causes my other devices like ps3, wii, etc. to have lower signal even when they are very close to the modem.

If I change the channel to other channel that doesn't have any interference (example: 9), then my other electronics will get 90%+ signal strength.--The iMac will get 0. If the channel is set to 1, then iMac get 3 out of 4 bars and other electronic equipment will drop the signal down to 50%.

Any help in resolving this issue would be greatly appreciated.

Thanks

Your modem router according to Motorola has switchable radios. In other words, it can broadcast on either the 2.4 or 5 GHz frequencies. It sounds like you may be using the higher band (5 GHz) which usually does not broadcast as strong a signal as the 2.4 GHz. Try switching frequencies. Read your Motorola manual and learn how to access all the settings from your iMac. Make sure you have an ethernet cable attached to your iMac before changing any settings for wireless.

I am broadcasting at 2.4 GHz.