This week's book giveaway is in the OCPJP forum. We're giving away four copies of OCA/OCP Java SE 7 Programmer I & II Study Guide and have Kathy Sierra & Bert Bates on-line! See this thread for details.
The syntax looks correct. Did you type any other switches along with avd? Try adding -verbose and check the logs on the terminal; maybe that would point to something. For e.g. try: emulator -verbose -avd my_avd3