Ok this might be old knowledge but I just found out about it and wanted to share this bit of knowledge with someone that may have had the same problem as me. Here is the scenrio, I was at my son's first Motocross race. I decided it would be cool to video tape his first race, since the way my nerves were that day it might have been his last race. Anyway I proceded to video tape his holeshot with my Sony DCR-TRV250 I have had this camera a while but really only used it a couple of times. All of a sudden I got a small arrow type icon similar to the eject icon, and the error code c31.23. What a crappy thing to have happen while it was a milestone of my sons racing career.
Well I manage to find a quick fix, the technical tap or rather smack. In my frustrations I smacked the camera pretty hard and low and behold it worked. Well it was a big pain to wack my camera all the time, so it pretty much retired to its bag. Where I did not pull it out very often except to see if it by some miracle was working normal again.
Today I decided to throw it on the charger and try to see if I could find a fix, and I found this Thread after alot of reading about how everyone wacks their handycam, I found a post from a user named Meredith. The suggestion was to open the tape deck of the camera and look to the right. Below are the steps to follow.
Open tape deck, make sure there is not a tape in it....
About midway back there is a black rubber roller in the middle of 2 metal guides.
In the center of this black roller you should see a white plastic tube, this is a bushing to allow the roller to move with out wobbling.
If you do not see this white tube yours has fallen out, so the search for a new one begins. Don't freak out a straw for a can of compressed air will work, or from a can of WD-40 will aswell. Simply push the new straw firmly into the center of the black roller.
If you see the straw take a small flat head screwdriver and press down on the top of the bushing firmly, I heard a click but you may not it just depends. Anyway this should fix the problem it did mine, and I am happy one my camera works and two I am smarter than Sony :)
Note if this does not fix the problem your bushing may be cracked find a pair of needle nose pliers and pull out the old bushing and replace it using the straw from a can of compressed air.
I hope this fixed your Sony Handycam 31.23 error code, now you are free to archive your lifes great adventures.