LoadGenerator STOPs participating in scenario

I have a strange behavior where one of our load generators runs okay for the 1st 8-10 minutes of the scenario-test, and at that point it stops running/participating in the scenario. This is a scenario that was running okay for the past 1-month with that same load generator.
I have tried all of the following: reboot load-generator; re-create the scenario; re-install the software on the LG server.
I have also checked that the service is running okay while this is happening, and have run 'netstat –bav' to make sure the ports are active.

Any idea what is the cause?

Thanks,
Ayelet.