does it works fine with a single monitor ?
For me it sounds like an issue where your 4090 is in high load ( of course a guess, with given informations ).
While you reinstalled the game, did you clean up the settings too ?
Have you checked the UserCfg.opt file , whats the setting for “FullScreenResolution” ?
You can also open the windows event viewer and check the error message, may be it give more informations.