I have been Googling (hah, the irony) for people who have had similar things happen, and it looks like this happens far more often than you might know. It seems like a lot of people have been banned or disabled without any specific reasons or warning. In fact, I found this:
How To Get Banned From Google Adsense In Just 2 Clicks
This is the only thing I can think that may have happened... and even this isn't really against their Terms & Conditions. Let me explain...
See, there's this thing called "NAT". NAT allows you to have many internal computers which all have the same IP address to the outside world. This means if I am using a system inside of my work, or at a Starbucks wifi, or at a public library, or even on certain ISPs, I will have the same IP address as many, many, many other people. If some of those other people just so happen to be users on my sites (for example, if they played in my gaming clan) they will have the same IP as me.
So, if I log in from one of these NAT systems to my AdSense account to check on the current totals, and they browse the sites and potentially even click on the ads, BOOM! According to Google's idiotically designed software, I have just violated their Terms & Conditions. Wonderful, no?
What's that you say? Wouldn't it be smarter to just ignore the clicks from those IPs? Probably... but it seems that Google's shite code that runs behind the scenes at AdSense wasn't designed that way... It seems that the developers overlooked one of the most fucking common ways people browse the fucking web!
They haven't replied to my request for information as to what they think I did wrong, so I don't know if my theory here is correct... But I bet it is.
Well, fuck them, I'll take my traffic elsewhere...