Yup... Some keys combinations mean other keys don't work. If you keep them pressed anyway, your computer will start beeping (through the PC bleeper)
Happens in any program, just try to press that combination in notepad for example... Like skidracer said, that's why many keyboard games use the CTRL and ALT keys, since the modifier keys (ctrl, alt, shift, etc.) don't lock out any of the 'normal' keys.
So... long story short, it's the same hardware limitation that has plagued PC's for the past 20 years... Nothing you can do about it, other than to pick your key assignments carefully to minimize possible conflicts.
Happens in any program, just try to press that combination in notepad for example... Like skidracer said, that's why many keyboard games use the CTRL and ALT keys, since the modifier keys (ctrl, alt, shift, etc.) don't lock out any of the 'normal' keys.
So... long story short, it's the same hardware limitation that has plagued PC's for the past 20 years... Nothing you can do about it, other than to pick your key assignments carefully to minimize possible conflicts.