Problem when printing from SDCard

I have a Prusa i3 with Repetier Firmware (I'm 95% sure... since it's not me who installed it) and everything works ok when I print by PC, using Repetier Host.
But, with the same Gcode, when I use it in a SDCard, well... my printer do a mess. It tries to park at (0,0,0) disregard if there is something underneath it... which has lead to some broken pieces once... also, it freezes at 99% of the print (as the LCD shows me).

Any hints to what I should do?

Thanks in advance!

I had similar issues. Check to make sure that when you save the gcode to the sd card from within Repetier that you have it include the start & end codes. It's possible that you have necessary start codes configured in Repetier (such as homing, bed leveling, etc.) that need to be included when you export.