arduino opens in different sketchbook than the sketchbook stated in Preferences

Hi

I have arduino 1.0.5 installed on Ubuntu 12.04.2. I've set File->Preferences_Sketchbook to a location where I have a bunch of sketches. When I restart the arduino gui it comes up with it's location set to a folder in my /tmp directory (it is called sketch_jul20a). When I select Sketch->Show Sketch Folder, it pops up a window showing that sketch_jul20a folder in my /tmp directory. This my be due to my lack of arduino understanding, but I thought if I set the sketchbook location in File->Preferences, that is where it would default to? Am I missing something?

Thanks...