You have a south bridge problem. Your box got hot enough to probably loosen some solder or it's bridged
solder joint. http://m.xbox-experts.com/errorcode/E04/0010/
Check the link out to help out man. I have used this site to help me repair several problems with my jtag.
I am also going to add a heat sink to my south bridge, ana, ram, and nand chips to keep them cool enough
to keep from rrod any more.