There seems to be a glitch in N360 where the little pop-up message that says "...virus definitions are out of date" pops up twice. Whether you click on the "X" (to close it) or wait for it to close itself, it immediately pops back up a second time. (After closing/being closed the second time, it seems to stay closed.)
(Clearly, this must be a glitch, as there is no intelligent reason for forcing the user to close the same message box twice in a row. So... just letting you folk at Norton know. This is with Norton 360, on Windows XP SP2.) ;p