http://www.archivum.info/microsoft.public.excel.programming/2007-05/msg00291.html
I had this problem (2003 add-in functions not being recognized by 2007) for a long time (see URL above) and, because of it, went back to EXCEL 2003. Right now, I am not seeing the problem (using another machine with 2007 on it) and am wondering if you folks still are or if, perhaps, it was finally fixed. I do recall that it changed to N/A only sometimes, not every time, so perhaps it's just an intermittancy that hasn't shown up again yet.
