I am trying to enjoy this game, but I cant even get past the first level!
Im actually stuck trying to double jump. I just cant do it! It says to press the jump button and then just press jump again before you land. Well I have been trying like crazy doing just that, but to no avail! I cannot believe this. I feeel downright stupid.
Could anyone shed some light as to what the hell I am missing here? I am using the keyboard.

Could you post the contents of the duke manhatten project config file?

# Duke Nukem MP variable config data
# Default Sound
uset s_device "ds8"
uset s_3d_emulated "0"
uset s_sfx_enabled "1"
uset s_music_enabled "1"
uset s_balance "0.5"
uset s_mix_rate "1.0"
uset s_sfx_volume "1.0"
uset s_music_volume "1.0"
uset s_speaker_type "0"
uset s_provider "DirectSound3D Hardware Support"
uset s_mix_freq "44100"
uset s_reverse_stereo "0"
uset s_persistent "0"
# Default DirectX 8 Settings
uset dx8_tex_filter "4"
uset dx8_tex_detail "0"
uset dx8_tex_quality "0"
uset dx8_gamma "1.000000"
uset dx8_fullscreen "0"
uset dx8_acc_tmatrix "0"
uset dx8_displayrefresh "0"
# Default OpenGL Settings
uset gl_ext_env_add "0"
uset gl_ext_edge_clamp "0"
uset gl_ext_lock_arrays ""
uset gl_ext_multitexture ""
uset gl_sync "1"
uset gl_displayrefresh "0"
uset gl_tex_filter "4"
uset gl_tex_detail "0"
uset gl_tex_quality "0"
uset gl_gamma "1.000000"
uset gl_fullscreen "1"
uset gl_ext_enable "1"
uset gl_acc_envmap "1"
uset gl_acc_tmatrix "0"
uset gl_cva "1"
# Default render options
uset r_displayrefresh "0"
uset r_ext_enable "1"
uset r_renderer "default"
uset r_device "dx8"
uset r_mode "1024x768x32"
uset r_tes_aggresivity "5"
uset r_tes_level "6"
uset r_acc_envmap "1"
uset r_acc_tmatrix "0"
# Other defaults
uset net_udp_default_port "7777"
uset net_tick "0.03"
uset name "player"
uset g_profile "player_duke"
uset gl_sysc "1"
uset m_invert "0"
uset m_sensitivity "1.0"
uset m_filter "0"
uset g_mapinfo 1

Could you post your system specs now as well as your OS. I suspect your computer is more then capable of handling this game though if my hunch is right.
Second could you go into the game and toggle the console while in a level, it should toggle by pressing ~ or the buttong bellow escape, above tab and left of one. Once the console is up could you type toggle r_timings it should now show you a frames per second display. Try double jumping again and tell me what your frames per seconds are when trying to jump.
If its the bug I think it is the frames per second will be rather high not allowing the game to register the second jump before you are able to press it. Then we just need to work out how to set a limit on your duke nukem frame rate.

gonna be honest with you, i have been using only my xbox 360 controller as a control interface and I have had no problems whatsoever with it. it was amazing because it works magically out of the box.

I have the original game on cd, not from GoG.
But, from my memory, you can only double jump while 3/4-100% on the up-jump.
You cannot double jump if you are already falling from the jump.

Running XP, 3GHz Core2, 4GB RAM, ATi 4850 etc and so on.
Im getting everything from 250 to 333fps so quite high indeed.

Force V-Sync?

That should not matter.
I played it with my E8600 + GTX280 machine, on XP64.

ARe you running in windowed mode? I notice that I can double jump whiles in full screen but not in windowed mode (always prefered full screen anyway so it's fine by me) give it a try?

I have a similar problem. Sometimes I can double jump, other times I cant, its very strange. Ive tried rebinding the key, no avail. Im on the first subway level, and I cant reach the babe because it wont let me double jump to the platform! (unless of course there is another way. Maybe I should try a 360 controler as one poster above mentioned...)
Sarabihyena, Im playing in full screen mode so I dont think thats the issue.
Stats:
Core 2 duo E6600
2 gigs Ram, DDR 2 800
EVGA GTX 260 (core 216 superclocked)
Windows XP Pro

It happen the same to me. It seems that window mode is the problem.

It's indeed the windowed mode. Double jumping works fine when i'm playing in full screen mode but i can tap the jump key all i want in windowed mode, it just won't double jump.

In case someone is following this topic and doesn't read the newer ones, double jumping works for me in windowed mode if rendering is switched to OpenGL.

anybody have save file for this game? I just reformat my PC but i can't figure out where the save file was stored. So i end up having to play from the beginning again. Before i reformat my PC, i was at the beginning of Chapter 8 playing normal difficulty,