Disable project scrolling

I'm quite new to IntelliJ IDEA, transitioning from Eclipse but I'm using PHPStorm for web development. I'm having this problem that when I'm scrolling in my project view and it doesn't let me scroll any further for some weird reason. I have to close some folders for some reason, can someone tell me how to disable this 'feature'? It's annoying the heck out of me.

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Original message URL: http://devnet.jetbrains.net/message/5506218#5506218