This has been asked a lot. I can't get my device running with ADB on MacOSX. I know this is a software problem, because I can connect via the Samsung application Kies.
see
1) adb not finding my device / phone (MacOS X)
2) Android device is not recognized in adb
3) Why won't Eclipse/adb detect my Samsung Galaxy Tab device on my Mac?
Possible solutions of which none worked for me.
details
OSX 10.8.0, Eclipse Juno (4.2.1), Android 4.0.3, apropriate SDK #15
Edit: Tried on Windows 7 also. Update firmware. Nothing working.
So finally I got it. I thought I was in debugging mode, because Android has this weird greyed out checkbox. I could activate USB testing mode, and now it is working.