iPod Shuffle not charging?

Mrs is feeling fat and frumpy and wants to go out
running but needs some sounds; bought her a 2nd Gen
iPod Shuffle but the thing doesn't seem to be
charging, despite there being an amber light. Have
left the PC switched on (not on standby) with this
thing docked via USB but the amber light doesn't go
green after hours of 'charging'; PC isn't state of
the art but it isn't old either (P4 2.53GHz 512MB) so
I'm assuming USB's aren't the problem. Starting to
annoy me, so can anyone tell me how long an initial
charge is meant to take as I just want to load this
thing with music and do other things.

edit: checked my motherboard manual (MS-6533/G Micro
ATX Mainboard) and it says the USB ports are +5V, so
there should be sufficient power. Does this mean the
iPod is faulty?

Sorry, I did check the link but neglected to mention
that it made no difference at all. When I disconnect
the iPod from the dock and switch it on there is no
light at all; green, amber, red, just null as though
no charging has taken place at all.