i have a solution for ya - something i figured out a couple of months ago. it is something i have to do on my mac book pro to get maschine to work in midi mode:
0. turn maschine on to midi mode, shift > control
1. go to your mac audio midi setup
2. go to window > show midi window (if you are still on leopard or earlier, midi will be a tab)
3. go to the configuration drop down and make a new one, i called mine maschine, but the name doesn't matter.
4. switch from one config to a diff config and all your midi devices get refreshed, and midi mode now works perfectly!
let me know if that works for you dudes who are having trouble getting maschine into midi mode.