Connect to the UART pins using a USB to Serial connector. The FTDI ones are best (imho) and there is one for the RPi, called FTDI RPi:
http://www.ftdichip.com/Products/Cables/RPi.htmThen you can log in over serial ... it won't give ssh, but will give a terminal; through which you can change the settings on the RPi Arch ...
Alternatively, pop the SD card into another computer, and then edit the relevant files ...