Nothing connected with SSE Stuart. Unfortunately one only finds the problem by trial and error. Everything seems fine until bang- "Questviewer has stopped working". Trying to make Windows 7 compatible with XP doesn't work, I tried that a lot of times.
The more up to date questviewer.exe does really fix it. Without that I understand it is not possible to use the multiplayer either. Mind you I have not tried that as I am not especially interested in it. Sorry I could not give a specific mission for you to try, possibly one with lots of ships and waypoints, but then you wouldn't be able to check that as you would first get the dreaded message.
Regards,
Angus.
P.S. If you overwrite the first file below with the second one it solves the problem. The SS2008 file looks like a face, & the SSE file looks like a green triangle on a black background. The picture of my desktop shows what the two files look like.