4 rows of Blocks on lcd2004

[Stunzasr20]

Hi there
I have Prusa i3
I have had the printer assembled and control under repetier host in the manual control tab, all was ok and was working towards getting ready for the first print. It seemed to ok until not sure why but now when usb is plugged in and the switch is off on the printer I get the screen as pictured first, which seems ok. But when I power the printer via the switch the lcd 2004 has all blocks as second picture shows.
Any suggestions as to how I rectify this or what might be the cause (laptop, bad connections, firmware etc)
Thanks in advance

[Mark]

how about adjust the potentiometer on the back of the LCD? sometimes when powered on, it's hard to see the the informations.
and you can check this link too:
http://www.geeetech.com/forum/viewtopic ... 13&t=17040