I have two hampton bay redington IV fans... they have dimmable lights however, when the lights are dimmed they produce a high pitch hum.. any advice?

If still in warrantee, take them back. Otherwise, I would take everything apart that will come apart and secure anything that could be vibrating. If neither of those works, buy new dimmer switches.

It's strange because it's not like a vibration part or somethingand and doesn't make any noise when the lights are at full strength... I guess I can't avoid having to take them back...

Thanks

This is when you dim the lights with the remote, correct, not with a wall control? Is any other control hooked to the circuit? When you dim the lights is the fan speed affected in any way?

Are you using the proper light bulbs?

Here's some more information on ceiling fan troubleshooting:

http://www.ceiling-fans-n-more.com/ceiling-fan-general-troubleshooting-and-FAQ.php