Crossfader Problems

[floydnet]

Have been using Zulu for nearly couple of years now, through 2 or 3 upgrades, no major problems until a few weeks ago when crossfader start to play up. Until then I could click on arrow at either end of crossfader box and it would move smoothly over to that side but now it moves in small, very slow jerks, typically takes 15 to 30 seconds to move from centre to end.

 

Recently purchased Masters upgrade hoping this might solve this problem as well as upgrading. It didn't. Un installed, cleaned registry, re-installed, no difference. Does anyone have any suggestions?