I see this error when starting FSX, even after a full uninstall of GSX, restart and reinstall. After loading FSX again in same windows session after I don't see it anymore however. Also on my flight I lost the FSX ATC text and was unable to work with ATC until they cancelled my IFR then the commands came back again. Nothing was visible and pressing "1, 2, 3" etc. didn't have any impact.
I've uploaded a copy of the error message.
Otherwise GSX still performed normally.