When you come to use the Compile or Run buttons you find that the "Command:" and/or the "Working Directory:" entries are blank.
You may have installed PFE before the initialisation files were set up properly, or possibly your initialisation has been deleted. Either way, the best solution will be to re-install PFE.
When you try to save or re-name files you get a "Permission Denied" message.
The Most likely cause of this is that you have gone Over Quota or your Security Settings are Corrupt.