I assume you mean the Northbride (NB?).... it reads fn41. But that's normally the board that ships with the SN41g2 not the SN45g.
The fn41 also comes with on-board graphics , which my board hasn't.
So in summary... the board is labelled fn41/fn45.... CPU-z thinks is a fn41sp.... but the physical layout dosn't (no on-board graphics) dosn't add up.
If the wrong motherboard drivers are installed (fn41 instead of fn45), does that somtimes confuse utilities like CPU-Z ?