Hello altogether.
When I'm playing Alien Nations on my Win 10 PC and want to switch to menu screen the game crashes which is frustrating after 30 min progress.
Do you have any hints?
Thank you.

try using the "Escape"-button on your keyboard. Works for me that way...

Having exactly the same issue, sometimes it crashes, sometimes it not, no matter if I'm clicking the Options button or pressings the ESC key.

UPD: Disabling Fullscreen optimisation fixed the issue (Win10)