Force power off shouldn't harm your components, if anything, you'll probably lose some data if you were working on something.
This is a possible solution I found from an older thread, especially since the person in this problem had the same motherboard brand as you:
GB's have, in general, some problems with particular USB devices; at worst, they will cause inescapable boot-looping - only cure is simply to not use 'em... Curiously enough, I have recently discovered that this appears to be a chipset implementation problem; I did a couple Intel G's for some people (specifically a G31 and a G41) and they were completely immune - devices that I know won't work on an X48 or P45 went through boots just fine! That said, I doubt you've managed to find two such devices simultaneously - and if any iPod were a problem, I'm sure I'd have heard about it here by now - the whining would be endless!
I can suggest a couple things to try -
Go into the BIOS and, on the "Integrated Peripherals" page, your manual shows "Legacy USB storage detect", but later BIOS say "USB Storage Function" - either way, set to "Disabled"... This can be a problem, and the only time you need this enabled is if, on the next boot, you intend to either boot from a thumbdrive, or access one from the BIOS to do a flash or backup your CMOS parameters - once the OS has loaded USB drivers, it has no function, and is a known source of grief...
Unplug your front panel USBs, and try with just the rear panels for a bit - just in case of a 'lunched' connector...
Have you taken a look in Device Manager to see if the drivers look 'happy'?
Have you ever done the (obligatory) "Load Optimized Defaults' from the BIOS since you started it up?
Source thread:
http://www.tomshardware.com/forum/267846-30-devices-freeze-computer