Prusa i3 Rework (RAMPS 1.+Marlin) doesn't respond

Hello everybody! I am very confused with my problem so i would be most thankful if anybody would help me as soon as possible so thanks in advance!
I just finished assembling a Prusa i3 rework, electronics: RAMPS 1.4+NEMA 17+NEMA 14(Z AXIS)..., Firmware: Marlin 1.6.6 with an a geared extruder just like in the photo attached . So it works just fine (had some calibrations first and had a little problem with the extrusion configuration so that's another problem that i can deal with later) after i stopped where i can print a bad quality piece i returned the next day to find that my printer doesn't respond to Repetier Host's commands (only the bed can heat up) even though i verified the 12V to every power port...after i keep sending commands i receive the annoying "x commands waiting" ...I've changed the transmission speed and even re'uploaded the firmware...i disconnected the Arduino Mega 2560 from RAMPS nd verified its nominal performing and launched a test code to operate one stepper motor...And i replaced my PSU with another ATX just to make sure i give a good power supply .
So again i am really confused about this....what can happen in a night that makes all this mess???! please help
note: Am suspecting noise from a mess in the wires that can maybe fry some stuff in the board ( worst scenario )

Edited 1 time(s). Last edit at 06/05/2016 06:25PM by xdarko.

What's the thermistor readings for the hotend?

Just abt the ambient temp, 25 deg C

Plug your hotend heat element directly to power supply and see if the thermistor indicates new temperature if no change your heater cartridge is dead.