'Windows --> Table of Contents' does not open TOC

I accidentally closed my TOC, and I can't get it open again. Going to Windows --> Table of Contents doesn't do anything (no response at all). Clicking on the TOC icon does nothing. This happened to me the other day with my Toolbox, and I accidentally got it back again, but I can't remember how. (I had the same issue with the toolbox - neither clicking on the icon nor going to Geoprocessing --> Toolbox opened it). Thanks in advance for any help!

I'm using ArcMap for Desktop 10.2.

Laura