What is it?

TypeError: Error #1009: Cannot access a property or method of a null object reference.
at index_v23_24_02_2010_Title_fla::buttonsDays_mc_38/frame22()

Any idea what is it? I think something to do with my instance of movie clip. I tried to find it but I cannot. I can not find any reference to symbol, button…nothing.

I’ve got symbol with instance name buttonsDays_mc but what about the number 38…that doesn’t make sense at all…for me.

any clue…?