I really have no clue how this fixed my issue, but while this was going on, I was also having some really strange problems with the Lama helicopter. I fixed that by removing the XPUIPC plugin. Then I went back to the SR22, having forgotten to reinstall XPUIPC, and my issue with the RXP GNS went away. So, evidently, RXP does not like XPUIPC!
Anyway, thank you reaching out and looking into this. I do appreciate it! I love the SR22!