I'd almost love it if a brave soul could try updating the
libusb0.dll used by Kobo from version 1.1.4 to the current 1.2.6 nad see if that makes any difference (I've always been a big believer in current drivers).
The project is hosted here -->
http://sourceforge.net/apps/trac/libusb-win32/wiki and in theory one should be able to download the libusb-win32-bin-x.x.x.x.zip package, and then follow the instructions in
Device Driver Installation on creating the custom INF file for Kobo, and then the instructions in
Updating the Device Driver to install the new driver.
I caution though in that I'm not sure on how to revert back!