Unity editor is not selecting the correct text entry field

This possible bug is driving me insane. I have a gif showing what I happens when I click on certain text boxes to enter values. It seems to be offsetting the selected text box. I've seen similar problems on here but those fixes don't work for me it unless I go to debug mode, (Right click inspector tab and click debug).

I'm using 4.2 Free on Windows 8.

Maximising the window doesn't help, neither does loading a new layout, or even restarting unity.