1. Removed the checks for a selected timezone as the defintion has been changed for listbox to exportselection=0.
2. The check for valid file before changing timezone has been removed as only files are shown in teh list post the fix for issue #12
3. The status bar is now updated if the operation is cancelled, fix for issue #15 . Also a roo.update() ahs been added as at time the label content is not updated when call is made right after a simpledialog is opened.