I may have found the glitch that the message describes. Investigating further.
Alright, nothing seems to happen.
The way I "paused" was by right-clicking. It stops the game in its tracks, but breaks the level select area.
Nothing happened when I did, but if anyone wants to try more please tell me if you find anything.
I may look into this a bit more...?
Update: I over thought it. You just have to pause by pressing "p". Hurr durr... More details soon.
Alright, I've posted a video to Youtube showing off the glitch and the text. Check it out if you want :)
Have a nice day.
(The video is also listed freely on Youtube so it's also pointed towards people who haven't played the game)