Hi All,
After about 3 hours of trying I have found a reason for this critical shutdown.

To explain how and why it happened.
I have a layout on which I am running four trains under AI control, two passenger trainz and two goods trainz. I have the goods trainz doing turnarounds at each end of their trip and using the HORNZ command to signal to the supposed shunter that they have seen their signals as in prototypical practice. This causes quite a few hornz to be sounded during the turnaround phase of their trip.
The session will run with no problems for some time but then crash on about the third or fourth trip. At first I suspected the horn sound file buit eliminated it after a short time. I then suspected the HORNZ command of becoming corrupted, but after redownloading the command eliminated that reason. After more running and testing I came to the conclusion that it happened when two locos received the HORNZ command at exactly the same time. I then altered the session commands, cutting out all HORNZ commands and the session ran for three hours without crashing. To prove my theory I inserted a HORNZ command as the very first command on two locos and started them off at the same time, the session crashed imediately. It seams like if Trainz attempts to apply the same command to two locos or two items at the same time this will cause a critical shutdown. I thought others might like to know this as it may be happening quite frequently.
Cheers,
Bill69
After about 3 hours of trying I have found a reason for this critical shutdown.

To explain how and why it happened.
I have a layout on which I am running four trains under AI control, two passenger trainz and two goods trainz. I have the goods trainz doing turnarounds at each end of their trip and using the HORNZ command to signal to the supposed shunter that they have seen their signals as in prototypical practice. This causes quite a few hornz to be sounded during the turnaround phase of their trip.
The session will run with no problems for some time but then crash on about the third or fourth trip. At first I suspected the horn sound file buit eliminated it after a short time. I then suspected the HORNZ command of becoming corrupted, but after redownloading the command eliminated that reason. After more running and testing I came to the conclusion that it happened when two locos received the HORNZ command at exactly the same time. I then altered the session commands, cutting out all HORNZ commands and the session ran for three hours without crashing. To prove my theory I inserted a HORNZ command as the very first command on two locos and started them off at the same time, the session crashed imediately. It seams like if Trainz attempts to apply the same command to two locos or two items at the same time this will cause a critical shutdown. I thought others might like to know this as it may be happening quite frequently.
Cheers,
Bill69