Poor liffle fellow, Nitroclicks is a known scam, and deleting accounts when you are reaching minimum is a normal practice there.
All you can do is say byebye to jour $490 bucks, but do not worry you weren't supposed to get it anyway. Of course you can email them, even multiple times, but they will not tell you what you have done wrong - and if they do will not be able to prove that you are innocent. I got my account cancelled because they accused me of opening 5 accounts. How could I prove it is not true? They can easily forge their logs to show that the IP number is the same.
Now sit down, get a good stiff drink and sign up with a site that pays, there is a special thread with the names, you may also visit my site (oops, am I advertising?

) where you can find some info.
You can also visit gptboycott.com and read the comments about Nitroclicks. You're not the only one!