I recently posted about an issue with JBoss Developer Studio and the OS X Yosemite beta on my MacBook Pro. I also use ScanSnap manager with my Fujitsu S1500M scanner and had exactly the same issue with the scrollbar in the chooser. In the ScanSnap case it was scrolling to the directory that I wanted a scan to go to. The workaround is again using the arrow keys to move the directory but it is worthwhile to know of the issue and be prepared in case you are dodoing something that you might not be able to do twice.