I usually notice this error in the early part of the day. The error message replaces the "Worst Node of the Day" section. Here is the error message.

Internal problem occurred in get_picked_nodes You have an error in your SQL syntax; check the manual that correspond +s to your MySQL server version for the right syntax to use near ' 0, +1, 66, 1308753191 )' at line 7

My initial guess is that no one had down-voted a node yet for the day. But that could be baloney.

UPDATE: For me, "early part of the day" means ~13:00 GMT