This error message occurs when a command tries to write to a file that you do not have write permissions to (or if there's a file already there that you do not have permission to overwrite).

Example:

This error message indicates you do not have write permissions for the current working directory.

Solution:

Before you begin working in Maple, ensure that you have write permissions for the directory or file that you want to write to.  You might want to use a temporary directory, or as in this case, specify the base directory in which the file will be written.