Your camera range may be set wrong. Or, your starry background is a sphere that is clipping the fire. OR, the starry background is a plane and the particles are in a plane which is so close to the starry background that those areas near the edge are swapping what's in front and what's in back cause there's not enough precision in the zbuffer. I think it's likely the last of these three.
Set your camera range so that the ratio between near and far planes is as small as possible. ie, 0.1, 100 is worse than 1,100, or 0.1, 10.
This will correct any zbuffer issues, but you still need to make sure that the particles aren't actually at the same Z detph as the stars... int he same plane as them, otherwise they'll never sort right. So move the stars firther away from the camera than the add blended stuff.
Set your camera range so that the ratio between near and far planes is as small as possible. ie, 0.1, 100 is worse than 1,100, or 0.1, 10.
This will correct any zbuffer issues, but you still need to make sure that the particles aren't actually at the same Z detph as the stars... int he same plane as them, otherwise they'll never sort right. So move the stars firther away from the camera than the add blended stuff.