Hmmm. If you don’t have any music on your player that you care about, you can try to reformat it under Settings/Format, and then try to connect up after, seeing if that does the trick.
Otherwise, you can try to connect up via MSC mode regardless by switching the Clip’s hold switch on, and then pressing and holding down the center button as you connect the USB cable That should get you into MSC mode on the computer, and then you should be able to upgrade the firmware–perhaps that will get things to work under either MTP or MSC mode. If not, then you could transfer your music off the Clip back to your computer, disconnect and, then, reformat on the Clip, and again see if that works.
Actually, I think I would try the second option first (trying to connect up via MSC mode and upgrading the firmware), before reformatting; it could do the trick easily enough.