I had this problem. Tried changuing g-code, motor drivers, acceleration etc etc etc. It actually turned out to be a faulty y-axis stepper motor. Your problem looks the same, you can test it by swapping the y and x axis motors.by busyman - Printing
Yes, the herring was red. I entered the gcodes you suggested into the preamble box in Slic3r, and I'm printing again. Awesome, thanks. Not sure how I got the original code wrong-probably a cut and paste error. Also, it helped to realise what I thought was the wrong behaviour (picture Untitled) was in fact right, and vice versa! This was the first thing I've ever posted, and I'm really impressedby busyman - New Zealand RepRap User Group
Here’s a very strange problem that has got me confused. Has anybody got any ideas?? Using Ramps 1.4 on a Prusa Mendal ii, Slic3r and Pronterface on a Mac. Everything I created and made into gcode worked fine (or at least would produce a plastic ‘thing’), up until 31/12/2012… Then strange behaviour started. Here is a snapshot of pronterface starting a print of a gcode file I created in 2012 ohby busyman - New Zealand RepRap User Group