That's a new one, never heard of this problem before.
I suspect it has something to do with either your java version or your desktop/window/display manager. As you already found out you can't change the panel positions (unless you do it in the source code).
Since you already removed the eteks directory you also removed the settings/preferences file. When you start Sweet Home 3D this directory should be recreated again.

Start clean by removing your Sweet Home 3D install and a possibly recreated eteks directory. Use the 7.5 download from sourceforge
Extract it in a directory of your choice, for example in your home directory. Start Sweet Home 3D with the SweetHome3D-Java3D-1_5_2 script. This uses the java version that is included in the download and should work fine.
If the same problem persists it is not Sweet Home 3D. See if a different desktop or display manager has a different result.