Bukkit

What steps will reproduce the problem?
1./rankup
2.
3.

What is the expected output? What do you see instead?
To rankup to the next group. Server crashes

What version of the product are you using?
1.6.2

Do you have an error log of what happened?
no the error doesnt show up in logs for some reason

Please provide any additional information below.
it was working fine for months but after a server restart it just stopped working

I know this is an old post, but for future readers having this problem, here's the solution: Your rank prices have to go in order on the ladder. The next rank MUST cost more than the previous. For example, you can't have a player rank up to "Member" for $10,000, and then rank up to "Master" for $5,000. All the ranks must be higher than the last.

Even if your ranks are set this way, go through your configuration file again. I am running an OP prison server, so the prices are high, but I miscounted the zeroes. One rank was $100 million, then another rank further down the ladder meant to be set at $650 million was $65 million.

Hope this helped!