Are you sure you are not in a playlist on the shuffle that only has one song, and not the All Songs list? You can change the playlist by using the VoiceOver button on the shuffle (press and hold). Here's general info about using VoiceOver on a shuffle
If that is not the problem, try doing a Restore. Select the shuffle in the iTunes sidebar, under DEVICES. Over to the right, go to the Summary tab. The Restore button is there. This will erase the shuffle and set to to default settings. If there was some type of data corruption on the shuffle's storage causing this problem, a Restore should fix it.
As a test, load a small number of songs on the shuffle after the Restore, to confirm the problem is resolved.