Occurs with a Nvidia dual screen setup running the 177 driver and the X server set to display Separate X screens the drop down menu appears on the primary display when selecting a location instead of on the location desired.

1)  On the secondary screen, open the clock program from the taskbar.
2)  Expand the locations arrow and click the 'Edit' button
3)  In the resultant pop-up window select '+ Add'
4)  Under 'Location Name' begin typing in a location.

At this point, normally a drop down list of all locations that match the string entered will pop up so that a location can be selected.  This would be expected on the secondary display, however it shows up in the correct position on the primary display instead.

If I had to guess the clock application is likely referencing the drop down list from an absolute position, thinking that the active screen starts at and absolute position of 0,0 and renders the location of the drop down list from there.

I've also noticed this problem when trying to use the volume control adjustment as well; it appears on the incorrect desktop.