Default desktop switched from left to right and won't go back

[GizmoDVD]

I have two display's - 27" Thunderbolt and 23" Cinema Display.

At some point they decided to switch and my Thunderbolt went from being my default display to my "second screen". I can't seem to get Mavericks to put - and keep - the dock on the Thunderbolt (Left) screen.

Any help?

 

[priitv8]

Move the menu bar in the display arrangement preference pane. The display with the menubar is the main display.