If you are running a recent version of Ubuntu and you need to use SQLDeveloper you will likely run into a problem where SQLDeveloper will load up as a blank window. This is due to the recent iterations of Ubuntu enabling Compiz in the default installation. There is a known problem with Swing applications not displaying properly with Compiz enabled.

There are two options. If you can live without the extra visual effects then you can simply disable Compiz as follows:

1. Navigate to System -> Preferences -> Appearance
2. Go to the Visual Effects tab
3. Select "None"

If you would rather keep Compiz enabled because you like the wobbly windows then you can try the following:

1. Open up sqldeveloper/sqldeveloper.sh in a text editor
2. Add the following line before the last line in the script.
   

export AWT_TOOLKIT="MToolkit"

You may have to use "MToolKit" with a capital K, but the lowercase was what worked on my machine running Ubuntu 8.10.

Gnome applets are set up so that there are a few applets with absolute position on the left side of the panel and a few applets with relative position on the right side of the panel. It is set up this way so that when the panel resizes the right-side applets will move relative to the right edge. The problem arises when you try to move any of the right-side applets. Once you try to move an applet it assumes you want it to have absolute positioning.

Instead of moving it visually on the panel follow the following steps.

1. In a shell run the command: gconf-editor
2. In the dialog navigate to apps/panel/applets
3. Going by the names you should be able to tell which applets are on the right side of the panel. For each one make sure that panel_right_stick is checked.

The position value is a 0-based index of the position from the right of the screen. So the right-most applet will have 0 position, second right-most will have 1 position, and so on.