After flashing the CFE, you have to tftp the DD-WRT firmware (DD-WRT Version for your router) ONLY not the Linksys firmware !!!
If you use the CFE, you can only put DD-WRT firmware on it, no web interface will be available yet.
You must also reboot after flashing the CFE, then tftp the DD-WRT firmware.
After tftping the DD-WRT firmware, wait 2 min. before you do anything, then try and goto the web interface, and or reboot..