[racket] Requirements for OpenGL?

Hi!

In the beginning of January I was playing around with (Dr)Racket a bit and wrote
some very simple OpenGL program (flying polygons and whatnot) that I based on a
"Hello World"-kind of example that I found here:
http://lists.racket-lang.org/users/archive/2010-October/042474.html
Everything was working just fine and I pushed it to some git account for backup
purposes.

A few weeks ago I decided to play around with it a bit more and cloned it again.
However, it wouldn't work anymore. If I remember correctly, I got an error
message along the lines of "no GL context available" at the following position:
(define/override (on-paint)
  (with-gl-context           ;;   <-- here
    (lambda ()
      (draw-opengl)
      (swap-gl-buffers)
    )
  )
)

After some (quite unsuccessful) research I figured out that some of my Linux
distributions packages must have changed (not (Dr)Racket though!) or something
like that. Hardware-accelerated OpenGL was always available though.

Yesterday I found some time again and decided to give it another try. And now it
works again. I am a bit perplexed.

So I guess my question is: What are the exact requirements for Racket to be able
to provice a "gl context" to a running program (not necessarily just on Linux)?
And what could have gone wrong that during some time the program wouldn't work?

Best Regards!