The requirements page of PhotoPost states that Safe Mode needs to be turned OFF to use PhotoPost.
This is because safe mode, by default, does not like users uploading files to a server and executing commands on the server.
In order to get Safe Mode to work, you have to configure PHP to allow file uploads and command execution.
Try doing a search, this has been discussed many times.
Please do not PM me for support or sales questions. Thank you for your understanding.