Corbu Theme is not supported for this application

Hi Experts, We are on SAP Portal 7.31 and on SP6, we have tried applying Corbu Theme but on logon page we see a red Message on top as '"Corbu" Theme is not supported for this application, Please see SAP Note 1681286'. Please suggest. Does corbu theme has anything to do with browser versions like IE 8 or 9.0 etc. we have checked with both IE8 and IE9 versions as both versions we are getting the same message. Please find the screen shot attached. Thanks Satheessh