data type xml: error importing xsd

I'm using version 6.3.4 of the performance edition. Want to use a variable of data type xml. Can't import xsd-file. Getting following error: ".... xs:element must be followed either by an attribute specification, > or />...". I'm using a publicly availabe xsd that definitely does not contain any errors. Nevertheless I checked the file as well. Where is the error? Cheers Thomas