Strange thing happened to me also, I mixed the two rendering solutions. But I figured out what the problem was... So If you use Backburner, "Distributed redering" shouldn't be enabled in the corona render settings. Because if you do so, a slave gets the job (one frame) from backburner, with the settings that it should use distributed rendering. this way frames get mixed.
So use eihter Backburner (to render more frames, and one frame per slave), or the built in CoronaDR (to render one or more frames, with rendering all the slaves the same frame, the same time).