Strange problems as always

Flash is weird...
I've got two calls:

_root.scroll.startsida.anim1.gotoAndPlay("build");

and

_root.scroll.startsida.anim1.gotoAndPlay("vanish");

They are triggered with buttons and I've traced so I know that the code is actually read. There are no loops, and no if's, nothing special.

Here's what happens:
First time I roll over the button, "build" is played. vanish is not played, and the second time, build is not played neither. When I put a trace in the buttons, it reacts every time.

So flash gurus... what can possibly be wrong?