HELP random movieClip behaviour

One of the movieClips on my stage keeps dissapearing when i run the fla. Flash is still registering it (i can trace out its co-ordinates, alpha, visible, width, height etc.) but it’s not visible on the screen and other movieClips wont interact with it. Iv’e checked its at top of visible area etc. and from all i can tell it should be visible but its not.
The movieClip is using a class file i wrote which was working before.
Basically what happened is it was all working, there was as on the first frame referring to the movieClip. I accidently added a keyframe to the wrong layer (the layer with the mc on, so the mc was no longer present in the first frame). I compiled and tested and i saw what i had done, i presumed it was just becaues the mc was no longer present on the first frame. I undid the changes and now it continues not to work. I’ve made no other changes and it’s really weird. plz help!

EDIT: OK i did some more testing and its as if its no longer registering it’s class file, when i try and trace out any of the class variables i just get returned undefined. I still can’t figure out whats causing it.