FLASHEFF2 ERROR: Target must be a non-null DisplayObject?

Hi,
all I like to do is set the alpha of the dynamic txt mc that has the effect applied on. I tried to make the dynamic txtfield with the FlashEff2 a movieclip and then set that mc's alpha, but then I get the following error:

FLASHEFF2 ERROR: Target must be a non-null DisplayObject.

Please advise.
Thanks!