PoP seems to select your maximum refresh rate without asking you. I tried multiple times to change the refresh rate of it without success.
If it is doing this, it means the EDID data of your monitor is being fetched incorrectly and is listing a higher refresh rate than your monitor is capable of. Try and update your drivers so the correct maximum refresh is shown, or use a tool like Rivatuner to create your own monitor driver.
Basically it's likely PoP is trying to select 75hz when your monitor can only do 60hz.
Doesn't the DirectX overrider works ?
For those who don't know what's the DirectX override:
-click Start then Run, type in "dxdiag"
-click the "more help" tab then "override"
-select desired refresh rate (eg 60)
-start the game
There's also an application which could be perhaps used to lock refresh rate which is called "RefreshLock" http://www.pagehosting.co.uk/rl/
It worked for me in other games when I needed it.
it needs to be setup at correct refresh rates though
-start up refreshlock
-uncheck "Always use the fastest frequency for mode"
-go to the 1920x1200 line and change it to 60Hz
-leave the rest at "0", leave the application open or in systray
-start the game
Unfortunately I can't try those myself as I don't own the game yet