shutterbug

how's the stage lighting?  how's the lighting on that speaker?  is there enough contrast on the speaker for the D50 to lock focus in dim light?  you know...I wouldn't expect D50's low light AF is that great...

shutterbug

There's not much you can do in photography if there isn't enough light because no light there'll be no photography period!

However, you have some options: larger aperture lens (i.e. f2 or bigger), high ISO (with a body that has relatively low noise, probably a high end one...sigh), shine a continuous light on the speaker, luck - set to continuous mode and shoot a few shots at once.  Other than those, I don't think you have another choice.

At that point, it's the guy with the best gear wins!