Sonoita was down from 2011-01-19 through 2011-01-22. A belt had broken on the dome drive. If you have images from 2011-01-18, you should look at them closely as we don't know exactly when the problem occurred (it might have been a day or two earlier!). Let us know if you have earlier images that look like they were "domed", so that we can update our records.
Arne
Links:
[1] http://www.aavso.org/forums/variable-star-observing/aavsonet
[2] http://www.aavso.org/category/tags/aavsonet
[3] http://www.aavso.org/category/tags/sro50