It also loaded fine when I went to look at it.
A couple of things to look check:
What type of graphics card do you have?
Is your graphics driver up to date? If not, you should update to the latest available.
In the 3D viewer after you have loaded your Jt file, please RMB, Select Performance->Edit... and look at the Troubleshoot tab. What version(s) of OpenGL are listed (left and right of the slider) - try moving slider to both extremes to see if it helps.