Guys, thanks for all the help. I reinstalled KSP and the mod, and now I'm having a blast (literally xD). Weapons manager works now. So much that I had forgotten another plane somewhere near the space center, and when I took off I was able to target it, shoot it down (I overkilled it with 3 homing missiles lol) and then started to shoot the parts of the plane that flew in all directions. I'm happy. Thanks.