Weird error #1010: I found a solution but

I just want to share this strange problem I had with flash. Basically I was applying some filters to a XML var. In flash everything worked well but on Internet it gave me this error:

TypeError: Error #1010: A term is undefined and has no properties.

After changing the way to apply the filter the problem was gone

Old

for (var r:Number = rowMin;r<=rowMax;r++){
rowMC += myRows.groups[r].movie	
}

New

rowMC = myRows.groups.((@num >= rowMin) && (@num <= rowMax)).movie;

Both do the same.

What happened? I have no idea. The import is it is working well now