Believe it or not, slap it (gently) in the side where the tape is inserted... I had the same problem, and found a website where lost of people gave this advice, followed it and my camera is working OK.! I also thought this was unbelievable...

Wow! I can't believe it! I smacked the tape side of the camcorder and it worked! Thank you!

I tried it slapping camera. then it is doing well. Thank you. I am saving of my money to repair camera,

If you're not crazy about whacking your camera ( I'm not) try this: Eject your tape and gently turn the little white spindles on the tape that winds the tape to take up any possible slack. just a 1/8 of a turn should be enough. Worked for me. I beleive the C:31:23 error code is a "crinkle" error message where the tape tension is not 100%, so it thinks the tape has jammed. probably an design problem with Sony where the tolerance setting is too exact. My TRV 510 still rocks!

Can't believe it!!! I had the same error message and I pounded the crap in anger a few times like this says, more than a mere tap, and it's working again. Go figure.