Location hierarchy tree widget doesn't work with Firefox

The location widget tree view has a bug, where by you have to click on the plus beside the location name twice before the sub-locations are displayed. It first time you click it the menu collapses,and you have to click to choose a location again. The location tree widget works properly with Internet Explorer 9, but doesn't work right with Firefox 7.01.

This happens in my current implementation OpenMRS Version: 1.8.2 Build 21762 and on the web demo, Version: 1.8.2 Build 23773.