Get a midi monitoring software to see if anything useful is coming in.
I use http://www.snoize.com/MIDIMonitor/ but its for mac. I'm sure you can find something similar for PC.
You need a clear note on / note off message.
Try using the midi library Arduino Playground - MIDILibrary
I guess its a stupid question but have you completely enabled the interface in able tons prefs/midi?
I had some issues when doing similar things of the notes being complete enough to be recognized as notes by the midi interface (the led blinking) but the serial data was incomplete and it was not a real not on/off as far as ableton is concerned.
And install a driver for your usb interface if one is available...
F