How do you approach debugging something you can't reproduce?

Question

I've made a simple OpenGL application (link). There you can see an image of how it is supposed to look - and how it does look on my computer (OSX):

Problem is: when my client clones and compiles it on his computer (Ubuntu), this is what he sees:

wrong http://dl.dropboxusercontent.com/u/62862049/Screenshots/wl.png

I'm really puzzled with that. This would be no issue if I could reproduce the bug, but not being able to do so make me clueless on how to even start fixing it. How can I approach this issue?

Answer 1

How can I approach this issue?

I suggest using VirtualBox to create a virtual Ubuntu environment on your machine, so that you can compile and debug the issue yourself.

If it runs as intended on your virtual machine, then the issue is probably driver-related on your client's side.