Midi Keyboard is triggering wrong note

hi there... i seem to be getting the wrong midi note event in Logic.When i press any of the keys on my midi keyboard, i get the wrong note..for example, i'm pressing c1 but its showing B0 on the note event. its as if all the notes have moved up one note. as a result when i load up a sampler like exs 24 or ultrabeat, the first sample starts from the C sharp note instead of C1. i hope i explained it clear enough, any help would be appreciated...thanks