JDeveloper Data Control palette is missing
In day-to-day use JDeveloper always make some weird things by itself... Here I'am showing how to solve the most common one, the Data Control Palette got hidden somewhere in the darkness... Screen showing the Palette: Altough I was not able to reproduce the problem I know how to solve it, you just have to go to Window Menu and click "Reset Windows to Factory Settings", that'll fix some lost tag in one of JDeveloper configuration XML's.