This happens on Windows but not on the Mac version of the IDE.
When switching between Library and Inspector in the IDE (something the wonderful new design forces me to do quite often…) I find it very frustrating that the Library/Inspector forces me to “sometimes” click the right-hand panel once before responding to mouse wheel scrolling. After this initial click, scrolling works as expected - move the mouse over and simply scroll.
Windows 7 SP1 64-bit, IDE 2014r1.1