iPod Nano (3g) doesn't charge-only w/iMac. WTF?

[Soundhound]

Anyone know what could be causing this? It charges when connected to my powerbook, to a charger directly to ac, and to my car charger/fm transmitter. But when connected to my white 2.4ghz iMac, it just drains. And it looses the connection often as well, disappears from the desktop.

Arg. Help!

thanks

 

[mad jew]

Is it plugged into the keyboard? Have you tried a different port?

 

[Soundhound]

It was an unpowered hub. Der. Never mind.