Hi,
I second FSt1's response - you should always post the error message AND you
should post any formulas that are failing. You also should tell us the
version of Excel you are using.
Possibly you are referencing an entire column, which in itself is not
illegal in a range name but, if you then use the range name in certain types
of formulas, in 2003 or earlier, you will get an error. Many 2003
formulas/functions did not allow full column references, those limits have
been removed.