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.
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.