I am having the same issues. Running PT11.02 Mac OSX 10.8.4.
Im seeing this problem across all AAX Arturia soft synths (I have V-Collection).
What it appears to be is the plug-in window is losing focus, as soon as I shift off the PT application. Then when I click back on the plugin, the plug-in window doesn't activate (ie. the outline/top bar stays greyed out)
Sometimes I can't even focus/activate the plugin window by clicking on the bar at the top, it just stays unfocused which means I cannot adjust any parameters at all.