Powerpoint

I am trying to save a file I've been working on in Powerpoint, and I keep getting the message "Powerpoint cannot perform the requested operation because the associated media file is invalid or corrupt." Also, it has made my original saved file (about 15 minutes ago) Read-Only.

I had some audio files in the slideshow, and they all played correctly. I tried deleting them, and the problem remained. The only other things in it are pictures.

so what are the permissions currently on the file?

read only, they used to be read and write. I didn't change them, a software bug appreared to. even using a different name to save it didn't work tho