Lee,
I had something weird happen. I was generating a 1600x1200 image (Disk video mode, passes=1) in a Windows XP batch file, and doing an automatic save every 10 minutes. After about 40 minutes, I noticed that it did the fourth automatic save after line #1195. A few seconds later, when it finished, the file was completely gone! (I've never seen this happen in DOS.)
I've set up a batch mode test case where the disk video image (1514x1110 to adjust the time) generates in 3 minutes and 0.87 seconds. Using an automatic save time of 3 minutes performs one auto save and works fine for me. I was not doing anything else on the machine at the time. Is it possible you were doing something that was using the hard drive at the same time as the saves were occurring? Jonathan