I would suggest using foobar for it's ability to interpret cue files and convert simultaneously.
Medieval CUE splitter v1.0 has split TTA files for me before. But you still need to convert to a usable format for audiosurf, so that's why I'm suggesting foobar.
Other possible problems are that the cue file is not pointing to the correct file (wav instead of tta), or the cue sheet's in S-JIS not unicode. You can always change the cue sheet's source filename to get around the character set problems.
One last thing to look out for is the pregap indices which are sometimes just plain wrong. CUE splitter will warn if the pregap is way too big than it should be, which is a warning sign of this. You can avoid any problems by keeping the pregaps: Since I can't remember which checkboxes have to be used, I guess you'll just have to experiment and verify your choices.