SB Live cards have some MIDI issues with newer versions of Cubase software. Creative doesnt really help too much, but if you check under their support section, I know they have a document listing off some of the midi problems and possible solutions
Some people have had luck using the non creative APSLive drivers, to give you both ASIO capability, and fixing MIDI problems
people.freenet.de/apslive/index1.html
You go in hard, and you go in fast.