After some discussions on the libusb list, and some testing on my Fedora 8 test system, I can confirm that the wakeups patch being applied to some Linux distributions version of libusb-0.1.12 (ie. Fedora libusb-0.1.12-wakeups.patch) breaks operation of the Eye-One Pro instrument. This is because the patch breaks the ability to acess two endpoints from two different threads. (Note that this patch is a CPU usage optimization rather than a functional bug fix.) My advice is that Argyll should not be linked with a system supplied libusb-0.1.12 with libusb-0.1.12-wakeups.patch, but that the version of libusb included in the Argyll sources (and which have been tested against all the supported instruments) be used until such time as such patches are removed or corrected. Graeme Gill.