Allow the time span to remain the same as you switch from standard to protrader graphs.
Keep the same time frame that was set in standard graph when you select protrader graph(or visa versa) for convenience. Usually you will want to use both graphs in the same time frame. If not, then you can simply readjust it to what ever timeframe you want.
This issue has been fixed in VectorVest 7, as ProTrader and Standard graphs have been combined into one graph type.