I installed the V2 of GSX for P3D v4 yesterday and ever since then I can not run P3D with the following message after installation: NANA.GUI detects a memory leak in windows manager(4) windows are not un installed
Never seen that message, and nobody ever reported this before. I cannot even find any traces of that message in the Prepar3d website/forum so, it's not clear if that NANA.GUI (which is a C++ open source library that developers can add to their apps to detect memory leaks) is part of P3D itself, of something used by another addon.
Try uninstalling GSX and reply YES to the question "Do you want to remove the Addon Manager ?", and see if P3D now starts again.