Mega ADK showing up on USB but cannot connect to serial port

I am attempting to program a Mega ADK on Ubuntu 12.04. Connecting the board to the computer goes smoothly, and it shows up in /dev/ as ttyACM0. However, when I open the Arduino editor, serial port is grayed out, and when I click on Tools > Serial Monitor it has an error because it is trying to read COM1. I went back and redid what the guidelines in have said and I have attempted to look up problems on the Forums with Mega ADK and Ubuntu, both to no avail. Anyone have any idea how I can fix this?