solidworks becomes transparent

I've got a client who's solidworks (the program itself) becomes transparant the moment when he starts 3d sketch< and he then can't work in solidworks and has to close it and start it up again. does anyone have a idea what can cause it and how to fix it, even the repair doesn't fix it. we haven't try to uninstall and do a fresh installation again as it is the last thing we want to do.

thanks

SolidworksGeneral