It's most likely that "invalid clicks" have occurred. If you clicked a few times on your own ads, this is why. It could also be a competitor intentionally try

It's most likely that "invalid clicks" have occurred. If you clicked a few times on your own ads, this is why. It could also be a competitor intentionally trying to take you down. They just simulate automated clicks from the same IP on your ads. In this case you would have no control, and Google would yet be justified in destroying your account because of the activity that your participation in their network is generating - even if it is through no fault of your own. This is one of many reasons why Adsense is not recommended. Another reason is that fact that they take so long to pay. No one pays on Net-60 anymore, except Google, because they can get away with it. You are lucky though. In many cases, they wait until you've sent them a ton of traffic for 60 days - just before payday. They then tell you that you aren't being paid, close your account, and refuse to provide a reason for it. There is no indication about how much (if any) of the traffic you aren't being paid for is being refunded to the advertisers. I'd suspect it's not anywhere near 100%. I'd suggest you join a CPA network that pays weekly and then choose advertisers from their inventory.