Old time simmer, but just getting back to it with msfs after a long absence.  Had product for a couple days and frame rates were typically 50-60fps.  Today I decided to configure my MS Sidewinder X6 keyboard and Logitech G400s mouse.  Downloaded software for both but now if I click the mouse once the flight has started, frame rate drops to 5 fps and cannot recover.  Uninstalled both aforementioned software, rebooted without mouse, used different mouse - all numerous times.  Now at wits end.  Using an xbox controller while my new stick is on order, that seems ok to pan camera and do what it does.  Just the mouse stops everything.  MSFS 2020 is a sream version.  New PC built for mfsf.  Was working great until now. 

Anyone have a suggestion?  Thanks.

After much hair pulling (hair I can't afford to spare), I found issue.  Somehow GSYNC got enabled on Nvidia card, and refresh rate moved back to 60hz.  Fixed and works now.