Flash 8 Textfield scrolling display problem

Hi Everyone,
I have been working on a recent project and it requires a dynamic text scrolling horizontally like a marquee. When i use a small amount of text then it works smoothly. But then the text goes up to say around 800 characters or so. Flash 8 doesnt control the animation smoothly enough and it seems jumpy. Any feedback is welcome.

I have selected “Ani-alias for animation” and the scroll the movieclip in the OnEnterFrame event using _x-=2; equivalent to _x=_x-2;

Please guide me.
Many thanx in advance.