I wrote to Mike about this, but thought the rest of you should be aware of this problem. I just spent about 2 hours trying to figure this out. I was using the PROMPT feature of Quicksat to predict for 3 satellites with no trouble. Then I tried to predict for each of them separately. The first worked ok, but the others locked up my PC. I thought the problem was in the whole element file (I use several) or in the individual elset, so I tried several different combinations. Some individual elsets worked, some did not. I had to reboot after each lockup. When using the problem elsets together with a good one, there was no problem. I couldn't figure why an elset would be bad by itself but work with another one. I finally found that the problem was with the Quicksat.Mag file. If predicting for a single elset, that NCAT has to be in the QS.mag file, otherwise the computer will lock up. If predicting for multiple satellites, at least one of them has to be in QS.mag. The others don't have to be listed. Aside from this frustrating problem, PROMPT is a great feature. Thanks to Mike for adding it. Jay.Respler@Genie.com Freehold, New Jersery