[Q] Lost fastboot access topic

Last night I unlocked the bootloader of my lte tablet running 2.1. Since unlocking it I lost fastboot access in bootloader. I tried everything I can think of, reinstalling naked fastboot drivers in both android and bootloader after purging anything resembling old drivers and alternatively tried getting fastboot access on a macbook and Linux laptop. In all cases my shield is recognised by adb while in android, but not after the reboot bootloader command. It seems so unlikely I broke fastboot access after a successful unlock, I hope someone can offer some ideas of what could be going on.

Thanks a million!