Have you been able to connect before with the usb cable you're trying now? Even though the usb cables are supposed to be universal some of them won't allow you to connect to the computer although they do let you charge. Try using a stock motorola cable. I tried a LG cable before and couldn't connect. The HTC cable works for me though.
For me CM9 is much better with Data but AOSP works with USB. Another workaround is to go into recovery and mount USB with an SD card inside. It doesn't work without it for some reason.