Between MATLAB 6.5.1 (R13.1) and 7.0 (R14), the Mathworks changed the behavior of the COM interface to MATLAB. The LabVIEW MATLAB Script Node uses the R13.1 compatible behavior. The problem is with passing real values to R14. Complex values work correctly.
Workaround: Change the types of input terminals of the MATLAB Script Node to complex datatypes.
Solution: NI will post a KnowledgeBase article with a permanent solution when it is developed.