I'm with Inky - my DD7 can do the simple math facts fine, orally, or with a computer game, but put those 40 simple math problems in front of her on paper and have a "race" to finish in a minute and she freezes. It has gotten so bad that she now does feel that she is "bad at math" because she was getting the lowest scores in class. (And yes, the whole class knows because the kids correct each others and then call out points to let the teacher know if they passed or not!)
We finally got the teacher to accept the fact that she can do this stuff, but won't when there are really only 10 different problems being asked 4 times to be solved in aminute. So the teacher finally agreed to let her just do 20 in a minute before going on to the next letter of more simple, tedious problems.
With DD she also says that she just can't write her numbers messily enough to get them down quickly enough to pass all 40 in a minute. We've actually worked on her writing numbers messily to try and improve her score, but she couldn't stand writing them that way and that slowed her down even more! crazy