The most common reason for being unable to load a message catalog is that the user has too many files open, such as if the user has an fopen() in a loop that has no fclose(). There have been some versions in which the MATLAB internal code for save() or xlswrite() have been at fault: if you have an older version and have either of those in a loop then you could run out of file descriptors.
If you are using linux then you might need to modify the process limits, what is reported with ulimit -n . However the default is 1024 for Linux which should be enough if you are not leaking file descriptors.
If you are using MS Windows, the default limit might be much much smaller, as low as 10 in very old versions of MS DOS.
