The waveform's and vectorscope's opacity values in the UV/Image Editor Scope panel might be wrong. Min selectable value shows 0.000%, max selectable value shows 1.000% - but i believe this max value was meant to show 100%, right?
From compatibility POV it'll be easier to not to draw "%" symbol (switching to percentages is quite simple but it'll break forward compatibility which better not to break without real need).
Fixed in svn rev44734. Thanks for the report, closing.