Not sure if anyone might have any ideas - I used to be able to charge my Xperia Z2 when the PC is turned off for the night - but after I had reformatted the PC about 2 weeks ago, I noticed that my phone is no longer being charged when the phone is turned off or in sleep mode.
I have checked, and the USB ports are charging all my other devices that are hooked up when it's switched off/in sleep mode - eg. it charges my wireless headset fine, but just not the phone... I have also downloaded and installed the latest USB driver for my ASUS motherboard in case that might've been the issue.
As a side note, if I plug in the USB cord into a little USB converter (http://ecx.images-amazon.com/images/I/21lPHO8VMtL.jpg - which is normally what I use to charge my PS Vita when my PC is off) then voila, my phone would charge fine even when PC is off/in sleep mode... but I didn't used to need this, so thought I'd try to get to the bottom of this if I can...
I've done a fair bit of Google searching for the past hour or so and tried to look up various things but to no avail so thought I'd drop a note here in case someone has a suggestion?
Make sure you have installed all available drivers for your motherboard and grab the latest versions from the manufacturers website rather than using any CD that came with it. The most likely cause is the chipset driver. Some motherboards also have a utility program to enable charging when in sleep mode and change settings related to it.