USB power failing on sleep

I'm using a mid-2010 Mac Pro running Yosemite. For most nights I'm not working I put it to sleep plus put hard disks to sleep when possible. Lately, I come back in the morning to wake the system with the mouse or pressing a keyboard button and it won't wake up. The mouse light is off and the caps lock on the keyboard won't turn green. If I quickly tap the power button the monitors come on and I can see my desktop but no keyboard or mouse function. I can unplug the mouse and the keyboard, pop them back in, and still no power. I have to do a hard reboot and then USB power for the front slots and back slots will return and stay on until an overnight sleep. Any ideas? Is the USB power failing on the system? If so, I'm sure I can just get a PCIe USB card but I do like having the multiple USB slots for SD cards and flash sticks.