Polyline/Offset tool sometimes does not generate equidistant polyline(s) correctly. Often, not always, only affects generation of the equidistant polyline(s) on ONE side of the original. A necessary condition to reproduce bug seems to be a polyline that contains a mixture of acute and obtuse angles between segments; number of segments, and whether figure is closed or not, also seem to affect appearance of bug. I have observed same behaviour in QCAD3 RC3 under Windowxs XP, and RC2 under Linux.