Usual problem - USB power has gone.
Where is the fuse located on the board? The reduced schematics on the RPi webpage does not show the USB at all.
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On this page there is a nice picture.
An addition to the soldering solution:
It is PP1/PP2 <-----> PP27
PP3 is GND, so don't connect this with PP27.
See full list of test pads https://www.raspberrypi.org/forums/viewtopic.php?f=28&t=89522&p=628505&hilit=pp12%2Bpp13#p628505
Raspberry PI disables power on USB ports on reboot. With this modification there is always power on USB port and no "hardreset" of usb devices by just rebooting possible.