Leave it to Larry (Airhogg) to find another FSX quirk.
SPAACARS failed to load Larry's flight plan with 1JY2 as a destination airport - resulting in an error. Larry sent me the flight plan and a copy of the error message. Upon investigation I found that the fsx-generated flight plan file had two periods between the file name and the "PLN" extension. This caused a failure of SPAACARS to find the flight plan file.
I also found that the airport name resulted in no file extension being transferred to the memory location in FSX for reading by FSUIPC.
Forum inquires with Pete Dowson (Developer of FSUIPC) currently indicate that this is another sim issue and that he will likely add a fix to later versions of FSUIPC to correct this. I will probably not change SPAACARS to fix this as it appears to be one airport name and only when that airport is the destination airport.
You can see the full exchange with Pete at the FSUIPC forums here:
So...for any pilot who experiences similar error the simple work-around until a fix in applied would be to rename your flight plan file by removing one of the consecutive periods in the file name before loading it into your simulator.