Switching workspace to open another project gives error.

I'm working on 2 different projects and I would like to switch from one workspace to another. When I switch workpace and try to open a new project, I get below errpr. Please suggest - 

"com.eviware.soapui.support.SoapUIException: Failed to load workspace:org.apache.xmlbeans.XmlException: Element soapui-project@http://eviware.com/soapui/config is not a valid soapui-workspace@http://eviware.com/soapui/config document or a valid substitution."