Giving the public link to a file is always done the same on dropbox.
Are you sure you've read the tutorial mentionned earlier
Anyway, this upload worked. I had to wait to download (megaupload...) but in the end it worked.
Ok so, when I toggle event 11 the condition "spawnerenemy.X >= scroller.X + 300", ennemis are spawned when the spawner goes to the left of the scroller object.
As expected I'd say.
It wasn't very logic anyway, you asked that enemies were spawned when the spawner is 300 pixel away from the scroller as well as when it is colliding with it (about the same X) at the same time.
Also, the "for each spawnerenemy" is not useful (even when you'll have multiple spawners created).
Also you would benefit of using a TiledBackground instead of a sprite in your layer0.
First thing would be to have a smaller background texture yet lengthen the layout/level at will.