Not a whole lot of other ideas. You're sure nothing has changed since the last time you used Photo Downloader? Camera Raw is 8.5 or higher? Bridge is 5.5 or higher? And it just all of a sudden stopped recognizing your USB connection to either camera? No Windows update?
Something either became corrupt or got mangled in some update from somewhere. You can try reinstalling the Camera Raw plugin. Get it here: Adobe - Adobe Camera Raw and DNG Converter : For Windows
If Bridge is otherwise running fine and it's just Photo Downloader, I'm hoping it's just a Camera Raw issue. You actually have a couple things to try with that. If you are at the very latest 9.1.1 Camera Raw, and reinstalling doesn't work, you can step back to an earlier version of Camera Raw, say 9.1 or even 9.0, and see if the update itself is causing problems for you.
Let me know. We might need to get a Windows expert in on this if it's the USB connection that Bridge is suddenly not recognizing.