My Roomba recently freaked out. I pushed the clean button but it didn't start cleaning. Instead it turned in a circle, beeped 9 times, then sat there. Pushed the clean button again, and it went through the same routine.

Turns out that when the Roomba turns in a circle and beeps 9 times there is an error with one of the sensors. In my case the "error" was a piece of plastic that had stuck to the sensor because of static.

So if your Roomba goes in a circle and beeps 9 times take a look at all of the sensors and make sure they are clear of debris.