S.I. Bass Guitar

With a new i7 2600K Desktop,The Studio Instruments Bass Guitar is behaving strangely.If I try to lower the "Pitch" even by 1 Semitone,with the "up" "down" adjuster on the GUI[the up,down adjustment,to the immediate right of the chosen "program" sound i.e. Bassman,Agressive,Default [Bass TONE/SOUND] The WHOLE Lowest/E string goes SILENT??? If I return it to "standard" i. e. A=440 the LOW string SOUND returns? I dont or have NEVER had this problem on my Laptop,or even when I used to have "Studio Instruments" as a stand alone application! What could be causing this[VERY loaded question ,I know] I REALLY dont want to have to Uninstall/Reinstall the whole of X1 Producer,especially now that X1c must be installed again etc etc and then Expanded etc etc.I may install the "Stand Alone" S.I. Pack and see,but this cant be used/loaded into X1 or can it? ALL HELP MUCH APPRECIATED,THANK YOU,RK.