i'm using an external keyboard with the laptop. seems like the error is related to the usb keyboard, but i actually did rebooted and unplugged the usb keyboard, booted BT5 again, this time no errors are shown... but still X doesn't start. it just falls back to the console.
The XKEYBOARD keymap cimpiler (xkbcomp) reports:
> Warning: Type "ONE_LEVEL" has 1 levels, but <RALT> has 2 symbols
> Ignoring extra symbols
Errors from xkbcomp are not fatal to the X server
(EE) SIGMACH1P USB Keyboard: failed to initialize for relative axes.
waiting for X server to shut down. ddxSigGiveUp: Closing log