Recently my Domino Designer refused to work properly, showing an error in the Applications view.
The solution was removing a faulty project entry from wsInfo.xml located in workspace\.metadata\.plugins\com.ibm.designer.domino.ide.resources
The file was valid xml. There was however ONE entry which had no replicaid value. When I removed that entry, Domino Designer started working again.
Please make Dsigner more robust by making the parsing of wsInfo.xml more resilient.