Thanks for the input, Gary.
Terrain Sculptor (TS) must deal with all versions of Flightsim. Since Simconnect doesn't apply to FS9, it provides an explicit interface via FSUIPC.
For simplicity of coding, TS defaults to FSUIPC when FlightSim is running when TS is started. If FSUIPC is not installed or throws an exception, TS attempts to determine which, if any, version of Flightsim is running. If it finds a Flightsim window, it connects via Simconnect. Whether or not FSUIPC is installed on the target system is irrelevant since the FSUIPC Client .dll is included with TS. If no version of FS is running, or if TS is unable to connect, then it retries every second until a connection is made.
If Flightsim is not running at startup but FSUIPC reports Flightsim running in response to one of the 1-second ticks, TS will connect via FSUIPC. However, given the way in which Flightsim starts up, it is likely (a certainty?) that TS will discover a FlightSim window has been opened before FSUIPC "kicks in" and TS will attempt to connect via Simconnect. But, if that fails and FSUIPC is installed, TS will connect via FSUIPC eventuaally.
So, as far as I can tell, "all bases are covered". I appreciate there may be more than one way to "skin this cat". But, if someone sees "holes" in that logic, please let me know.
As regards this particular user, I am at a loss to explain what happening, since FSUIPC does connect if Flightsim is started first. However, it does appear to be a local problem since no one else is reporting such difficulty and I have tried, unsuccessfully, several different way simulating faults to induce the issue.