Update error

Norton Internet Security 2012 pops up a message saying that my virus and spyware definitions are out of date.

LiveUpdate says it updated 22 seconds ago.

I run LiveUpdate again (and again and again)—directly or by clicking on the Fix button.

LiveUpdate completes successfully and says so with green.

Immediately, I see the same popup warning.

Sometimes I see an NIS window that has Fix Now at the top, under that "Fix not complete," and under that a list, in which the only entry is Protection Updates . . . Not Fixed.

In addition to the usual activity on my computer (Windows XP, Lenovo A52), Carbonite is doing an online backup. Carbonite has been running for two days without this error message.