SmartSDR crashes when monitor goes to sleep or wakes, can't tell due to lack of visibility. But please not that PC is not set to sleep, but is set in power settings to run 100% of the time. I use windows 7 on i5 NUC computer with all updates installed.
Is SmartSDR actually crashing or just disconnecting from the radio? If a true crash, could you post a screenshot of what you are seeing? This might help us to understand what is going on. Without that information, the others are on the trail of the most likely scenarios for this kind of issue (power management, power saving mode, etc). I understand WH6HI has this already checked this, but I include this here for others that may run into this same problem.
I've been running dual monitors that go to sleep after 2 hours for 3 years will all versions of SSDR including all the ALPHA for the past 2 years with out a problem. I have set everything the like network adapter, USB ports etc to never go to sleep or to go power saving mode. The only thing that shuts down are the monitors.