suddendly dead machine and problems with comunication

[cesare candela]

Hi! I'm newbie.
I've assembled my prusa I3 pro b according to assembly manual, looking at all the images.
Now, I have three problems

1) Yesterday, when I turned on the machine, main board fan has been whirling all the time and using the lcd panel I was able to move the x, y and z (this one with problems, see above) with the command Prepare/auto home. Notwithstanding the correct installation of drivers and software, the last version of control software wasn't working at all. Today, when I use the same command from lcd nothing happens. Fans aren't working. Nothing. NOTE: MAIN BOARD AND LCD SEEM FEEDED BY THE USB CABLE, INFACT THE GREEN LIGHT IS ON AND THE LCD TOO, EVEN IF THE MAIN INTERRUPT IS SET IN POSITION "OFF".

2) the repetier host software doesn't communicate with printer. Cblae driver seems properly installed and clicking "connect" in the software it seems be connected. In the log file appear letters and numbers like "N10" etc etc...but no command is received. Com port is set on default values (9800 baud) printer on 250000 as suggested.

3) Z rod give me problems, but I have found probably a solution on this forum..

NOTE: cables are fixed in places according to images and cable colors as depicted in assembly manual.

PLEASE HELP ME.