Furforce

I have a HUD that everytime I try to attach it, it would show on screen for a whole half second and then disappear and would say "Worn on Invalid Attachment Point?" This is incredably fustrating. How do I fix this??? EDIT: I tried attatching the hud to diffrent spots, tried attatching it to my avatar, I even tried attatching it on a diffrent computer all together. None worked. I use the SL3 viewer.