your first problem is with:
onEnterFrame = setInterval(fadeFrame,100,mcName);
that should be something like:
fadeFrameI = setInterval(fadeFrame,100,mcName);
your 2nd problem, if you decide to use setInterval(), is you must clear it:
// do whateveer
third, it's not clear you're executing that code on the _root timeline. if you're not, you should use _root.mcName, instead of mcName to pass to fadeFrame().
The onEnterFrame worked find when I had the instance name of the movieClip hard coded rather than passing a variable(mcName) into the setInterval.
Even when explicitly setting the _root.mcName when calling setInterval, it doesn't function properly. A trace confirms it is getting the movie clip. The movie clip is attached in the onRelease function before the gotoAndStop() that is sending the file into this frame.
show your corrected code.