The dreaded "Modified File" problem

I opened 10.3.4 and suddenly have many clips with the big red "modified file" warning label. I have not even edited them yet. I found previous threads on Apple coms suggesting to delete the Transcoded media folder and deselecting "create optimized media" in Prefs. I have tried this trick with no luck. If I reveal the clip in finder, the original media plays fine in the QT player. So I tried reimporting with no luck. Then I tried duplicating the original media with a different name to a different event and importing and it still comes in with "Modified File". How do I get the original media into FCP? Do I have to convert it to another format? Stuck...