If the bed and other motors are going backwards/forwards, the board could have test firmware on it, rather than something like Marlin.
Seems like the SD adapter was either on the wrong pins (shorting out the supply) or has a fault.
FYI: The way the voltage rails work is as follows: RAMPS provides (+12V) power to the Arduino Mega. The Arduino Mega has a regulator on it that provides 5V for the Arduino Mega as well as +5V power back to RAMPS. If you somehow short out your 5V rails on RAMPS, the Arduino Mega regulator will either die (smoke) or shut itself down (depends on how much of a short it is, if it's an original or clone, etc).
Seems like the SD adapter was either on the wrong pins (shorting out the supply) or has a fault.
FYI: The way the voltage rails work is as follows: RAMPS provides (+12V) power to the Arduino Mega. The Arduino Mega has a regulator on it that provides 5V for the Arduino Mega as well as +5V power back to RAMPS. If you somehow short out your 5V rails on RAMPS, the Arduino Mega regulator will either die (smoke) or shut itself down (depends on how much of a short it is, if it's an original or clone, etc).