Check the Advanced Power Settings on the computer and try to set them as the attached picture shows (you can leave all the settings as they show and only change the one that is indicated). Also, disable the screensaver since turning the monitor off should do the trick.
If the AHMI project running on this computer is the one with modified DF1 driver, which was discussed in another topic, does the AHMI crash while being used by the operator or while not in use? In my opinion, that project is a little bit heavy-weight for DF1 driver.
DF1 communication, in general, might eventually get interrupted by some other events and have AHMI freeze or time-out and crash (you could try increasing the poll rate if this setup doesn't require frequent polls).
If this issue is AHMI related then modifying the project again might help (or make things worse
).
This would kind of conclude the suggestions that I have for you.