Hello, I seem to be having the same issue with double jumping described in this thread: http://www.gog.com/en/forum/duke_nukem_series/q_manhattan_project_double_jumping

I have tried all of the solutions described in that thread. However, no matter what combination of rendering device and window mode I try, I still can't get the double jump to work. This leads me to believe that my problem might be the one first suggested about the fps being too high (the op of that topic's fps was around 250 to 333 fps, while mine moves between 500 and 1000). So, does anyone have any idea on how I might limit the frames per second, and hopefully fix this problem? I can't seem to find a vsync option anywhere in the game's config files. If anyone has any idea how to do this, or knows another solution to the problem, any help you could provide would be greatly appreciated.

Ah, thank you for pointing me toward the control panel! I poked around and found the option to force vsync, and this totally fixed the problem. Double jumping now works as intended.

For anyone else who has this problem with Nvidia cards, the option to force vsync is in the control panel under 3D Setting->Manage 3D settings, at the very bottom of the list.

Thanks again for helping me solve this problem!

Glad you got it working. :)

Out of interest, what graphics card do you have (and other system specs might be useful too, like CPU and RAM). Only my machine didn't have the double-jump issue unless it was in windowed mode which the other thread mentions, and my hardware is about 3 years old (C2D E8500 3.16Ghz, 4GB DDR2, XFX GTX260 Black) so a lot newer than the game itself. I don't know what framerate I was getting, though.

My machine has an x990 i7 3.47Ghz, 6GB DDR3, and a pair of Nvidia GTX 580s. This is not the first time I've encountered a problem with new hardware screwing with older games, either. For instance, when I tried to play TES 2: Daggerfall the game would act like it was on fast forward because the processor was way too fast, and I had to download a separate utility to throttle down the speed to get it to work properly. The price of the latest hardware, I guess.

Yeah, that hardware is quite a bit newer than mine so I would expect your uncapped framerate to be quite a fair bit higher than mine.

An x990, when I Googled it, says it has 12 cores! So that alone, if all cores are utilised, is around 6.5 times faster than mine. Not sure how many cores the game would use, though, not whether it would max out any cores, but still, quite impressive.

If none of the previously offered solutions seem to work for you, I recommend changing the renderer in-game. I tried all the other methods, but my double jump was unreliable at best. Then, in desparation, I decided to switch from OpenGL to DirectX as the renderer. That did the trick for me.