"Unable to open workpaper" error when the Excel is open anyway

1.serach *.xlb and delete all
2.copy epace.xla from /pfx engagment/wm/utitliy to c:/progarm files/micfosoft office/office10 (the current version)/library
3.open Excel alone, Tool>allins make sure only epace is check and browse to officexx/library and copy it
4.regedit: currnet user-software-microsoft-excel and make sure "open" key point to the correct path