I had the same problem. Never before have I seen a login prompt when booting to a liveCD. I exited and started a new session and it came up OK, although slowly. I have been trying since then to install, but the installer always hangs up after a few minutes displaying the message "copying usr/lib/i386-linux-gnu/dri/r300_dri.so". When I cancel the install it says that "the installer is not responding". I don't know what to make of all this. The LM-201204 RC iso installed just fine, but I lost access to cinnamon, so I decided to wait for the final and reinstall. I'll try downloading the final version again to see if that makes a difference.