I rarely login to check my Google AdSense account, but I did last night and was presented with an error. The error was in a dozen plus languages, but the English version read:
The Google AdSense website is temporarily unavailable. Please try back later. We apologize for any inconvenience.
At first, I thought it was my network but it seems like it was very widespread and lasted at least a couple hours.
We have reports from WebmasterWorld and DigitalPoint Forums. The earliest report is at 5:01 pm (EST) from WebmasterWorld that AdSense was posting this login error. A couple hours later the login began working again.
I do not think actual earnings or live ads were impacted. There is a thread at WebmasterWorld with publishers complaining about low earnings, but that is probably just slowness in the AdSense reports.