pronterface error message

Hi,

I've test my reprap printer to run my first printing and it work well, and the next day I try to make another print and it act weird, it keep sending message as if i connect and disconnect in most of the time if i move my axis through pronterface. it also says "echo:Invalid extruderworkDir open failed" and everytime i send a command to my printer, it always show a message "valid extruder"
and if i hit the print button, it act nothing but my gen6d keep on blinking as if it was printing.

anyone have any Idea whats going on? I'm really curious since I can't do my second printing. the first print is just a line

Here is a video about the error on my durbie prusa mendel, the board is gen6d , any clue will be greatly appreciated , I'm really frustrated (
http://www.youtube.com/watch?v=5hDhgvbuqVM