Problem with Weapon Challenge?!

hi, i have a problem with one gun and the weapon challenge. kills with the M16A4 are not counting anymore since some weeks. i re-installed the game, it doesn´t help. what can i do?! thank you, GP
Here is a picture from ingame: http://www.pic-upload.de/view-32279090/wc.jpg.html
Here is a picture from ingame: http://www.pic-upload.de/view-32279090/wc.jpg.html
Comments
the M16A4 is the "designated marksman (single and burst)".
Once you're past this M16 challenge, the DM role will earn kills again.
This is probably the most common misunderstanding in how the weapon challenges work!
No kidding, it even got me at first