Well, if that's a space problem, it won't work for newer characters, right?
But it does work fine for new most of the new characters.. x_X
Well I guess I figured out the problem.
In the past I had another PvP Ladder which saved the Kills as PVPKills, and I saved them as PvPKills in my script.
Now rAthena seems to make a difference for the caps, but sql doesn't. That's why a player only can PvPKills OR PVPKills.
But when he already has PVPKills and I want to read or write PvPKills nothing happens.
You might want to check your database if you have some variables with the same name (but eventually different caps).