i have a similar problem, after a wipe data factor reset from safestrap and then flashing the thor gapps rom and making sure the rom slot was active(not the stock rom slot) but the rom slot that i flashed the thor gapps rom on and ,,,i rebooted the device as usual but it only booted to the grey kindle fire splash screen so i held the power button until it booted again but only going to the grey kindle fire splash screen again,,,so i tried to boot it to safestrap recovery using the volume buttons but it would only boot to kindle fire factory recovery,so i rebooted the kindle from there and back to the grey kindle fire splash screen it went, so i rebooted in to kindle recovery because safestrap was not coming up and it would only go to kindle recovery,so i hit the return the kindle to factory settings and when it was done it went back to grey kindle screen and thats all it will do,,,,when i plug it up to windows i get mtp in device manager,but the driver has an error saying device can not start error 10
and when i plug it up in ubuntu 12.04 and run lsusb in the terminal it comes up with an id and says Google Inc. but i can't get adb to recognize the kindle,,, i even checked adb with another android device to make sure it is all setup right and it worked,,,, i have read a few times in the forums here that you have recovered this device from many types of bricks and feel that if the grey kindle fire logo/splash screen is coming up that there is hope to get adb working,,,
any help is greatly appreciated and thanks in advance !!!!
oh and it's the kindle fire hdx 7 in tab