Each axis moves in one direction only (1 reply)

Hello,

just finished the assembly of my prusa with arduina mega and ramps 1.4.
Ad discribed in [reprap.org]
i used the arduino software Version 0023 for uploading.
The Ramps 1.4 Testcode works fine.
As shown in the How_to video i uploaded sprinter with the described changes.
In Pronterface (precompiled, July12th) i can move each axis in onla one
direction. Extruder, Hotend and Heatbed work fine.
If I reverse the axis in the Sprinter settings, the printer moves to the other
direction only. It always moves to the Pronterface "+"-direction only.
Pushin one of the "-" buttons just causes a kind of vibration in the motor
and to move it in "+" direction you have to axceed the distance you previously
tried to move it in "-" direction.
Any idea what could cause this?

Thank´s

Merty