It's amazing how reliant I've become on key strokes, especially when it comes to graphics editing. A few months back I noticed that holding down the shift key in Adobe Illustrator no longer constrained items to 45, 90, or 180 when moving and that spacebar + command didn't bring up the magnify option. My initial search yielded nothing, probably because my brain was mush and incapable of putting together logical search phrases. I haven't needed to do much work in Illustrator until recently so I tried the search again and low and behold, a solution!
Chances are that if you're having this problem you are Quicken user like me. It turns out that Quicken's One-Step feature launches a helper application that runs in the background. I had enabled this and hadn't though anything of it, but as it turns out, it causes conflicts with Illustrator's keystroke options.
To fix
That should do it. Happy vector art creation!