Hi Hans Thanks for the reply, a git bisect is needed to nail it but I've just not had the time. You cannot get a DMESG output as it causes a hard lock before any relevant messages can be obtained. Yes it's one of those unfortunately. See here for info: https://bugzilla.kernel.org/show_bug.cgi?id=91921 It works fine under Windows and worked before kernel 3.13.7 so it's a Kernel issue.