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.
JT is the common language of PLM and is the world’s most widely used 3D format. JT is the first ISO International Standard ( IS 14306-1) for 3D visualization and collaboration. Compact and accurate, JT is used throughout the product development lifecycle in all major industries to communicate the critical design information typically locked up inside a CAD file.
Siemens PLM Software customers rely on JT to be the most robust 3D visualization format available.