Truncated “Recent Items” Label in OS X Mavericks General Preferences
I had the same problem, and figured out the solution.

Apparently, for whatever reason, 3rd party hacks or something else, the font size in the preference pane was incorrect. Since there's no way to change the size of System Fonts in the GUI, I used the TinkerTool utility to reset to defaults.

It was the fixed-pitch font that was incorrect, and TinkerTool had it highlighted. I just hit the Set to default button in TinkerTool's Fonts tab and that fixed it.

I'm glad I sorted this out and didn't have to re-download the 5+ GB Mavericks Installer!