I'm having the problem of CatDV files constantly going offline. I reconnect the files and the next time I open the catalog many of the files are offline. No files have been moved or folders renamed. CatDV seems to simply 'forget' where the file is.
We're running on a Facilis system with the catalog on the same drive as the footage.
Look at the Media Path field (on the Summary or Other tabs, or elsewhere if you've configured your details panel layout). That's the path the file was originally imported from and is what CatDV uses to locate the media, subject to path mapping. If you moved a folder or renamed a volume or import on Mac and play on Windows or vice versa you tell CatDV in Media Search Path preferences what the old and new locations are so it will find the files automatically. If you double click a missing file it will prompt you to locate it and will set up a temporary path mapping but it won't remember this beyond the current session unless you save the path mapping or use the Update Media Location command and save the catalog to save the new path in the Media Path field.