It's not clear what you mean by "normal WB". Canon Auto WB does not work well with tungsten lighting. In DPP change the WB to the appropriate preset for the light source, or click on a known grey or unclipped white element in the image, or adjust the temperature to the best results. OTOH, AWB should give good results with flash unless it is only fill-flash and the primary source is tungsten or flourescent. If the flash is the primary, perhaps the camera is set to an inappropriate custom WB?
Off the topic, but DPP 1.6 is about three generations old. I'd advise upgrading (for free) to DPP 3.0, it is much better.