I have been able to get the MX-3000 editor to run and communicate under Windows 7. While I don't, by any stretch, claim to be an expert, this is what works for me.
1. You'll need "Windows Mobile Device Center" installed. There's a good step-by-step at:
[Link: adirob.blogspot.com]. Even though the blog is for Vista, the steps are pretty much the same for Windows 7.
2. Once installed (and the proper driver assigned in device manager) you'll need to make sure that Windows Mobile Device Center is running BEFORE you connect your MX-3000. It appears that if you try and connect your MX-3000 without the Mobile Device Center running, Windows 7 will try and revert to the standard URC USB driver which won't work. If it does you'll need to reassign the Microsoft USB Sync driver as outlined in the blog listed above.
3. Make sure your MX-3000 is awake before connecting the programming cable.
I have also noticed that if the MX-3000 editor is running before I plug in the unit it won't recognize the remote until I close and restart the editor.
Now, if only someone could point me towards a "Live Update" version of the software or a new database then I could complete my programming without having to "learn" every command from the old remotes.
Good Luck!