USB device drawing too much power

Just got this message, never seen it before. Got a cheapie hp mouse, Mac wired keyboard, and a hp printer (turned off) plugged into the back of the iMac, and a Mophie Juice pack air plugged into the keyboard's USB port. when I try to plug my iPhone into the keyboard's other USB port I get this message:

Because a USB device was drawing too much power from your computer, one or more of your USB devices have been disabled.
To prevent damaging your computer, the USB device drawing too much power has been disabled. Other devices may have also been disabled. When you disconnect the device drawing too much power, your other USB devices will be enabled again.

Anyone here ever seen this? Only happened with the Mophie plugged in, but it's never happened before.
If ya'll wanna see a screenshot just tell me how to take one.

Don't know why this got moved to notebooks, this is happening on iMac.

NOTE: Thread moved to appropriate forum. Not just anything goes in Anything Goes

Generally, the keyboard USB ports are for self powered or very low powered devices. I have my Logitech mouse plugged into one and my printer in the other and never overdraw power. However, when attaching my external hard drives or optical drive, I use the main ports.

Also, the iPod Classic, Mini, iTouch, iPhone, iPad draw too much power for the keyboard ports. The iPod Nano and Shuffle are OK. If you need more USB ports buy a good powered hub.

@chscag
Thanks for the advice, I never had this issue before and always used to charge the juicepack with the phone inside it (so it charged the phone too). But the juicepack has went unused for quite some time so it was beyond dead. Changing the plugs around now.

With all respect to advice already given, I think the best thing is an externally powered USB hub. There are numerous brands, some are better than others. Post back if you want more info about that option.