PE 9.I am close to finishing my project and get 4 media offline. What causes this to occur and what do I do about it?
Usually, Media Offline refers to broken links between the PREL (Project) file, depending on where the files are physically located. This ARTICLE goes into more detail.
Does anything in that article relate?
I think you might have moved the project file(may be from one computer to another) or the assets you are using in your project, so that the original path to the assets which existed last time you succesfully edited and saved your project, is now broken.
When you opened the project it must have asked for Where is the file? Locate the assets at that time
Double click the offline file in Project window and give correct path.