Perhaps this will help some.
I realized that this problem occurs on my Canon Optura 30 (consumer mini DV) when the tape is fully rewound. Tapes that are not rewound seem to work fine. If this situation applies to you, try the following, and make sure that in the future you don't fully rewind your tapes!
Fast forward your tape in a tape deck or rewinder. It should play in the camcorder now.
If you don't have a machine to do it for you, you can manually advance the tape with a pointy object and a pencil (the eraser--or your pinky!). On the back of the tape, near the top (that is, opposite the side where the tape is exposed), locate the notch between the two spools (the "wheels"). The notch will have a spring-loaded slider inside, which you can hold open to free the spools. Otherwise they are locked in place and you can't turn them. Holding the slider open with your pointy object, insert the eraser in the right-hand spool (i.e., when the exposed tape is pointing down and the "spine" of the tape is pointing up). Turn the spool slowly counterclockwise, making a few complete turns, to gather up a short length of tape, enough so you have a few seconds' worth of timecode. Be careful not to leave any slack. You can turn the other spool a little bit (clockwise) to catch any slack; lift the cover on the exposed tape (by holding back the little release) to make sure it is tight. If you're not sure which spool to turn, it's the one that does *not* have a window on the front side of the tape. (If the tape is fully rewound, the spool in the window should look full.)
Hope that helps, and good luck. In the future, I'll heed the common advice to use the camcorder playback as little as possible, relying on a tape deck for RW/FFand making sure to transfer material to scratch disks ASAP and then just storing that footage away in a shoebox!!!