Version 3.1 of WordPress has a lot of new updates which cause that the plug-in does not work properly. But within a few days another version of plug-in will be released and it should then work fine.
I apologize for all the inconvenience and thanks for your patience.
New version of plugin: KKProgressbar v1.3.2 Hotfix – Download: http://codecanyon.net/item/kk-progressbar/132862
= 1.3.2 Hotfix =
*FIX: Plugin has been adjusted to a new WordPress version (v.3.1)
*FIX: Corrected progressbar display in edit window