I think this is the same thing that happens to me now and again with 10.1. If you have a laptop and open the attribute table on an external monitor that is a different size than your laptop display it throws things out of whack when you open it when you are just on the laptop. This could also happen frequently if you use remote desktop from different computers.
If that is the case, you should be able to either connect the monitor that you were using or remote in with a higher resolution.
If that isn't the case, another thing you can do is reset all of your settings to default (which includes window positions). To do that, rename your 'Normal.mxt' to something else and ArcGIS will create a new one next time it is started. Unfortunately, that will also reset all of your toolbar settings and default toolboxes that are loaded as well.
For 10.1 on Windows 7, your Normal.mxt file is located at
C:\Users\<username>\AppData\Roaming\ESRI\Desktop10.1\ArcMap\Templates. I would expect 10.2 to be very similar although I can't speak to your Mac setup.