If you are in fact using the BETA build, then there is something called Assertions-error messages. Assertions-errors are a breakpoint feature that pauses the program and puts up an error. If you are using full screen, then you won't see this error message since it's behind your screen. I highly recommend running in a window, but full screen by maximizing the window. This will give you access to the task bar where you can see the error messages appear. To do this, click on the checkbox in Trainz settings where you choose the screen resolution and your display.
Once the error is on the screen, you then need to either continue, retry, or ignore. During the beta-testing, we were requested to screen capture the error message and then continue. We would then upload the error along with a detailed description of what was going on and what we did to cause the error. Sometimes, if we continued, the program crashed to the desktop and that was reported separately, or sometimes at the same time in the same report.
Since the product has moved on from the beta stage, I highly recommend upgrading to the latest build. It's far more stable and doesn't have the Assertion-error messages enabled.
On a more important note.
When you do crash, let's say to the desktop and need to restart, we highly recommend running a database repair if the program doesn't do that automatically. To do this, click on the Developer menu item located on the top of the Launcher menu bar (it's also in the same location in Content Manager) and choose Repair database.
If you were editing, choose revert when you restart rather than continue. The reason is if you continue with your current editing session, you may corrupt your route or session and be at a total loss. Reverting goes back to the most recent temporary backup, Trainz makes interim backups while editing in addition to your saves, and you can recover from there.