Win7 ultimate, i7-3720QM, gtx680m
Broken: 2.71 official and 0b4da96
when I rotated the bone, the cylinder is deformed well until 180 degree and then it flipped (also the bone)
just open the file, select the bone on pose mode and rotate it on Y axis on the N panel.
this is the file: http://www.pasteall.org/blend/31321