glOrtho problems

I am having problems using my glOrtho( ) call and I cannot figure out what I am doing wrong. I have a 3-D plot and initially my plot appears 2-D as I have a top-view of it, as if I’m looking straight down on top of the image. I have my rotations working so I can see I have peaks in my plot and my z-data does change. Right now my x and y data is working fine but something is wrong with my z data.

As I calculate my zdata I calculate a zmin and zmax. My zmin is -8.39231 and my zmax is 126.537. I also calculate these for my x and y data and inside my glOrtho call I pass in the mins and maxs. So my call looks like

 glOrtho( xmin, xmax, ymin, ymax, zmin, zmax ); 

Unfortunately I cannot see any of my points unless I make zmax a GIANT number. Right now I have to multiply zmax by 100000000000000.0 to start to see my data. Does anybody have any idea why I cannot just use my zmax value to put into my ortho call but why I have to multiply it by a huge number? :confused: Thanks for your help in trying to help me solve this problem.

Which matrix do you apply glOrtho to?
What are states of other matrices when you draw your data?