Yes, the strange thing is that you can see it in Excel, and in fact that GDI+ in Excel seems to bee seeing it too. I don't really know how this could be happening, and where is Excel getting it.
But once thing we should be sure first is that Excel is actually finding it. If you print to PDF in Excel, and then press Ctrl-D in Acrobat, do you see "Arial Narrow" or maybe Excel used a fallback font too?