Hi,
First, see if the Matlab Script Node is trying to open any files. If so, then make sure that the current Matlab directory is set to the directory where that file is located.
The error may also occur if there is a disruption in the script server between MATLAB and LabVIEW and the connection was never re-established (possibly by closing MATLAB prematurely). Close both LabVIEW and MATLAB then relaunch them both and run the VI.
Regards
DD