As you might know, it is possible to take screenshots in Freelancer without the use of external programs.
If everything works fine, you press "Print Screen" key and a BMP file with screenshot is created in c:\Users\%username%\Pictures\FreelancerShots\
This should work pretty much everywhere in Freelancer, from the MAIN MENU to the Bar on Planet Curacao.
Recently this stopped working for me.
And it appears that it does not work for others and has not worked for others in the past: Screenshots for Freelancer
Of course it is possible to take screenshots using external tools like Steam, Xfire, Fraps, programs associated with your GPU and many others.
But I decided to figure out why the native screenshot functionality was no longer working.
It turned out, that the culprit was Avast Antivirus Anti-Malware Shield.
Disabling this shield or setting Freelancer as exception in the shield settings solved the issue.