I've filed this earlier:
Bug in action:
But unfortunately it still happens in 6.0.2
This is one of my biggest annoyances with IDEA at the moment. The otherwise pretty stable and solid gui completely fails here with all the scrolling going on. I suddenly have to reach for the mouse, things move on the screen, bah.
Of course it would be great if this could be fixed but maybe as an interim solution it is easier to make showing the paths (the grey text (/foo/blah) after a folder name) in the project view optional. That is the only reason why the lines are so long and why scrolling happens I think.