As this is a new PC build (only 10 days old), no it has never worked.
Interesting thing though, if my desktop resolution is set to 1024x768 @ 88hz, then when I launch a game at 800x600, it runs at 60hz. If my desktop resolution is set to 1024x768 @ 85hz, then when I launch the same 800x600 game, it runs at 85hz... (and not, it's not a quirk with that specific game)
EDIT: After doing that testing, any game in fullscreen at 800x600 now wants to run at 60hz instead of 75hz...
EDIT 2: I was able to get 800x600 running at 75hz again by deleting my 800x600 @ 112hz custom resolution, rebooting, adding a custom resolution of 800x600 @ 85hz, and then finally rebooting again. Once 800x600 @ 75hz was working again, I was able to delete my custom 800x600 @ 85hz without consiquence and was even able to add my original 800x600 @ 112hz back in.@