I can do this, too - that is, fly from another airport TO KMEM. However, if I fly a route starting AT KMEM, by loading KMEM as the start airport, I get a fatal error. If I load to a random airport first, then load KMEM as the start airport, KMEM loads fine, and a complete flight works for me fine.
The big difference is either loading KMEM as the starting airport (fatal error) or loading a random airport first, let everything load in and settle, then select KMEM after the first random, but unnecessary, airport. I don't know enough about this error, or why it happens to give any other helpful info, yet.