Monitor Stuck in Interlaced Mode?

Sorry for the very long delay between posts, I am just incredibly busy... But, here's a problem I've just had to solve and I thought worth coming to these pages for... Ever had a screen stuck in interlaced mode?

So my monitor is an Asus MX27AQ, really nice screen, but I was part of Alpha testing of a game at the weekend and it had set the game into what appeared to be 1920x1080@60hz interlaced mode.  I have NO idea why the game did this, but it was all testing and work in progress, they had a report and I closed the game.

But, it left my screen stuck in a strange way, it wasn't interlaced it had gone back to progressive, but it was at 59hz not 60, no matter what I did with drivers or windows display settings it was stuck at a lower refresh rate, selecting 60hz just resulted in no change and the "Do you wish to keep these changes"... Nothing was happening, either accepting them or reverting them.

And the horizontal pixel clock seemed to be off, now I could not change this setting, either in the screen controls, windows display controls nor by removing and reinstalling the display driver nor graphics card driver, even removing all the settings seemed to leave the screen still in this situation... I reset it, re-powered it, disconnected reconnected... I did everything physical and software related.

Absolutely frustrated I then delved a bit deeper, and inside the nVidia display settings I found "Create Custom Resolution", you can get to it on your own nVidia card via their menu...

The key thing for me was to create an invalid resolution, so I just changed progressive to interlaced...

And hit that "Test" button at the bottom.

The screen went on the fritz immediately, but only for 15 seconds as I didn't accept the changes and the screen righted itself.

Properly righted itself, all the settings came back, the pixel clock skew was gone and I could see 60hz and select it for the display again.

I think this was a case of the screen itself holding onto some setting maybe on its own firmware... I'm totally guessing... and in kicking it again via the nVidia driver I cleared the bad settings out.

But, the did persist, over power cycles, over reboots, over removing and replacing the drivers and even taking the screen to another PC (in my case a laptop) I even changed from a Display Port cable to an HDMI cable.  The only thing to sort it out was the bad custom resolution and letting the display return to "normal".