The issue here seems to be that MATLAB is unable to find the PREFDIR or access the parent directory of PREFDIR.
The following steps might resolve the issue:
1.Type PREFDIR command in MATLAB command prompt.This gives you the path to the directory. Open up the PREFDIR using Windows Explorer.
2. Close MATLAB.
3. The folder which contains the PREFDIR folder would usually be hidden. Unhide this by right-clicking on the folder and choosing properties.
4. Once it is made sure that the folder is not hidden, restart MATLAB.