The message says something went wrong on the server, so the first thing to do is to examine the server logs.
There is probably an exception in the logs that explains what is happening.
The targeter file could be missing, or the file system could be read-only, something along those lines.
Alternatively the database that holds a reference to the file has an issue. The logs will give you all the details.
And if that does not help, I suggest you contact your system administrator :-)