Yes. That error comes from iconomy. Further up in your log you may see a warning about this. iconomy 6 has a huge bug where, if you are using file storage instead of mysql, if multiple things interact with your economy at the same time, it will cause an error that can wipe out your econ data. niji apparently refuses to fix it because you can avoid the problem by using mysql and he's more interested in getting ico7 out of beta than fixing ico6.