SoapUI import problems xml project from readyAPI

Hello there,

i have an occuring problem when importing a project (xml-file) to SoapUI (5.7.0 / 5.7.1). The project has been created in readyAPI. The error message reads as follows: "An error of type NullPointerException occured." 

java.lang.NullPointerException: Cannot invoke "com.eviware.soapui.impl.wsdl.support.wss.DefaultWssContainer.resolve(com.eviware.soapui.support.resolver.ResolveContext)" because "this.wssContainer" is null

I have been successfully importing the project before and tried figuring out problems with some TestCases by deleting some and trying the import again.Without success so far as the same error messsage occurs. Can anyone help me understand the error message or has anyone had the same problem?

Best regards,

Julius