This is a real milestone for me. I believe that all the hardware is finally working properly so I only have a couple of software issues to resolve.
I replaced the endstops last night with a set of spares that I had bought with the original Techzone electronics. I always figured that I would burn out one or two and they were cheap so I bought a full set of replacements. These are slightly different from the ones I am replacing. They have LED's on them so I can see that they are getting power and are working properly.
Unfortunately they don't seem to be doing anything. It makes no difference whether the optical signal is interrupted or not. I can jog all three axis in both directions even with a card inserted in the endstop. I think that this is an issue in the setup in Sprinter so I am going to look through the configuration code today.
I also need to reinstall Pronterface since it won't load an STL file. This shouldn't be a big deal since I have confirmed that my other computer, on which I also installed Pronterface, can load them just fine. I probably messed up the install of one of the several apps that Pronterface depends on so I will clean it all out and start the install from scratch.
As a final note I should mention that I started working with Sketchup 8 this week. I downloaded a free addon that allows import and export of STL files and I have been able to create a couple of fairly simple part files for items that I would like to print. I found it simple to learn and easy to use.