Finally solved this problem!
The mission file selection process via file chooser relies upon having network share access to the mission files.
The files were being locked via Samba from the Il-2 SSD client, and therefore when the server came to load them, they were unavailable for reading.
This is strange because the files are not "read" by my program, they are simply selected, so they shouldn't be locked. This may have something to do with opportunistic locking by the Windows Samba client process.
EDIT: Yep, confirmed it. When I add this to my share in my smb.conf it fixes it:
Code:
veto oplock files = /*.mis/