Hi Moxxy,
I hate to be redundant so very often, but if you've already replaced the cable that you were using; as suggested by [MENTION=140132]coltm4[/MENTION], there are two other things that you can check yourself, you decide which one you'd like to attempt first... You can pull the headunit and check the harness connectors, making sure that they're securely latched in their ports. The other thing that can cause a power loss at the USB-2.0 input is a frozen firmware condition where the communication through that port stops due to a damaged software file! To correct this issue, try pulling your RAD 20A fuse; which is the constant power (HOT AT ALL TIMES) to the headunit.
Pull out that 20A fuse and leave it out for a minimum duration of four hours; this will give the memory circuit an ample opportunity to drain, restoring the system back to it's default factory settings, and deleting the Temporary off-line history files, much like you would do your windows cashe after a hard reboot! PS: Be sure to leave that 20A fuse out of it's slot for at least 4 hrs or this procedure will not work. Upon returning the fuse back into it's slot, you'll notice that your preset radio stations will be gone! Please be sure to let us know if this resolves the problem so this procedure can be filed here so that others may benefit!
rig, cheers