So I was poking around in bios settings, trying to figure out why I couldn't boot with USB2.0 enabled, after a few restarts, BIOS stopped detecting any USB thumbdrive I inserted (even ones that worked before) so I did a Load Optimized Defaults. After changing what needed changing (non usb related) and restarting machine, suddenly I could boot my Lexar JD Firefly in USB2 mode.
go figure.... weird as...