So I ran into a problem when installing my Push. Windows 7 64bit didn't recognize it as a generic usb audio device. This is a problem for all devices using this driver. In certain instances, Windows doesn't install the driver on OS installation.
You'll scour the internet for solutions and really won't find any. It's not a problem with the Push or Ableton, so Ableton probably won't have a solution for you. But I did come up with one a while back while going through the same problems with a Quneo from McMillen. The Quneo wasn't for me and I've since returned it, but I did learn something valuable.
What's going on is that you're missing the driver from your OS. I've isolated the probable culprit. It's as easy as downloading a small .inf file and then dragging it over to the appropriate directory. No need for a reboot. It should work right away if it's the problem.
I posted this in the McMillen forum and here's a link to it.
If you're having problems, I hope this helps. I just got my Push up and running this morning after about 12 hours of frustration. http://forum.keithmcmillen.com/viewtopic.php?f=50&t=976