I use R4CCE to edit the dat. While it will save a db file, it won't open it for whatever reason. Just use this file (click here) and open the USRCHEAT.dat in the download in my sig, edit out the games you don't care about, select "save as".....in the drop down box, select db file to save as and save it as the cheat.db file. You should be good after that.
Hmm, i have the same problem, except i tried out what rayder suggested and haven't had any luck.
I save my cheat.dat(which has the same content as usrcheat.dat) as chat.db replacing the old one in the flash rom(btw, it does let me save as cheat.db, but it says "*.dat" in the box), but when i go to the game's cheat page, it says that there are no cheats for the said game. I checked and the game ID is what it should be(AVPC), and i only added one code(Max luck, which i converted from the us version to 01211F45 0000E4A9).
Btw, i als tried to save the codes as a text file, tried to activate them but the one i wanted doesn't work at all, and the moon jump works weird...