The jumppad should work allright. I tested it at home with a NVIDIA 6800 with recent NVIDIA driver for Linux and at the ofice with a GF2 with recent NVIDIA driver for Linux too, and the jumpad worked allright. While testing I discovered that jumping sideways or backwards I could even jump on the big column. Jumping backwards of sideways, results in a higher, further jump (!).
However, I have a laptop with a onboard Intel graphics chip. And on that machine all my jumps are lower. For instance I can't jump in the well in Smalltown, which is 5 cubes high, and I can't jump at higher level in Arena01 either.
I assumed that the Intel graphics chip, or the Linux driver for the chip did the opengl support wrong.
But you tod me you have a NVIDIA card too. So this is a interesting issue. Jumping seems to be different on different computers !
I assume you have recent drivers.
O ... deleted te readme.txt ...