To simulate the problem, just add an approach procedure on the g1000 and try to set an altitude at the approach fixes and press the “ENT”. Once this is done, the simulator simply closes to desktop.
Sometimes the altitude set, go to the last waypoint, try another one.
Yup. I was just about to report the same exact problem. I was hoping the problem with RNAV approaches generally not picking up the glideslope/VNAV was the lack of reference altitudes. So I tried multiple times on different aircraft using the G1000 to input the altitudes and every time I press enter for the selected altitude, I get the CTD like you.