Not quite sure if this is the right place for this, but it seems most relevant here.
but hey, I'm wondering why the volume scroller on my keyboard occasionally stops working when certain applications are selected.
I'm pretty sure this is a software problem.
Say for example I'm using Firefox and watching a YouTube video, as soon as interact with any of the flash player controls on the video, or if it's even selected, my volume scroller will cease to work until it click onto the volume control in the notifications area. This is just one example and in this case the program is flash player, but this happens when other some applications are selected such as Cities XL 2012.
It's as if the scroller is being mapped to something else, or not at all.