I've had the same problem. I don't get them everytime - but often enough. When I've been more regular about doing inversion, it tends to stop after awhile. I assume it's because I'm overdoing it.
Also, do you have high blood pressure? I've always wondered if it has something to do with my HBP causing small capillaries to bust or something. Aside from the cosmetics though, it never seemed to cause any problems. And again does go away when I'm inverting more regularly.