Congratulations Fyron (even though he took a random guess). You are correct it was a corrupted image file
A while ago i realised for some mysterious reason (unknown even today) that my game files reverted to Version 1.70. I had the Image Mod installed that allowed the unmodded game to use the image mods extra torps and beams. So i installed Version 1.84 and it overwrote the image mod torps and beams files. Thusly when it tried to fire the extra point defence beam it crashed the game.
So if anyone gets an error simmillar to this we know it's related to missing/corrupted picture files
Thank you for all your help btw guys. This i what makes this community so helpful and great