If I see the two trains moving toward each other at 1.5c, but each train sees the other train approaching at .9c then there seems to be a problem...

The observer will see the trains pass each other before the trains themselves think they've passed each other. In essence, the same objects will be in different places at the same time.

If I see the trains collide before the trains themselves collide...isn't that telling the future? In which case, the collision could be prevented...in which case I'm lost.

Thanks again.