When I zoom in or out in QGIS, my scale will only halve or double respectively. This is the case whether I manually type the scale into the window at the bottom of the screen or select one of the set scale options. The scale automatically jumps to the nearest scale that is an exponent of base 2,256 (the smallest scale allowable for some reason), where the exponent is a multiple of 2. For example, if my scale is 144,447 and I type in or select 250,000, it automatically jumps to 288,895. This is occurring prior to adding any layers. I probably just have to uninstall/reinstall but though I would check here first.