Here's what I have found out. The program does work. When the atmosphere begins rendering, the Windows Task Manager reports the program is not responding. The CPU was still working on the thread, so I let it go. When the draw update occurs, the task manager reports the program is running. When the program returns to the atmosphere calculation, the window jumps, and task manager reports the program is not responding.
I would open the Windows Sidebar and open the CPU gauge. Only run Terragen 0.9. Open the task manager to the applications tab. Watch both while doing a small render. The CPU gage should show that the CPU is busy. If on a small render, it does not finish in a reasonable time. Hit the thread here again. Good luck.