Textbox scrollbar problem

hello all,

I have created a textbox with a scrollbar. When I type in the
textbox in flash and it overflows, the scrollbar becomes active and i can scroll down the box.

Now when I try to import the text from a .txt file and there is
overflow, the scrollbar does not become active and i cannot scroll
down. Does anybody know how to fix this, or if it is a bug?

Thanks -