MountainMom - the problems you describe are quite familiar. We've certainly found that the combination of "math" that is really a writing subject (and writing is a problem in our house), combined with the boredom and lack of attention from too much drill, can add up to poor math performance. DS10 is a natural mathematician, but does not do well in what is called "math" at school.
However, what you describe is also a classic description of a highly visual-spatial person - great at conceptual math, poor at computation.
www.visualspatial.org/vslasl.php Not a learning disability (but, man it feels like it some days). If this looks anything like your DD (and I'm noticing that PRI!), it might help make sense of what feels like a major discrepancy.
Note that everything I've read about visual-spatial learners says that if they are having trouble with math basics (commonly times-tables as an e.g.), the solution is to give them more complex math, not take them back to drill....
