In lieu of trying to ascertain what has changed between LV versions (which, even if we found out, would not be helpful is it will not change) it might be a good time for a work-around. Ultimately you will need to provide a lot more detail as the specifics matter (for example - code that demonstrates the problem). I assume you have progressed this also with NI support with same code, maybe it is a case of wait and see.
Looking into your IPC issue, I see that there will be a few things to work out regarding how far you will be able to take impersonation without requiring the host process to be elevated (https://msdn.microsoft.com/en-us/library/ms172351(v=vs.100).aspx). The best option would be for the server process to run under a service or similar account (rather than admin) to better enable access.
