I had a similar problem when trying to follow those stupid instructions to make XBMC as my default dashboard. After i rebooted my xbox came up with a 'Your xbox is in need of service' followed by a bunch of japanese writing and red LED light. I then had to put in the Mech Assault game and softmod it again from scratch. Once that was fixed i then followed these instructions which were 'foolproof' and it worked
FTP the default.xbe and evox.ini in the E:\dashboard to the PC. This is a back up. Rename default.xbe to evoxdash.xbe. FTP evoxdash.xbe and the evox.ini to the C drive. If XBMC fails for some reason it will look for and load evoxdash.xbe.
FTP the "SHORTCUT by TEAM XBMC.xbe" file to the E:\dashboard folder. In FlashFXP you have the option to right click on the file and "transfer as". Use that option and transfer as default.xbe Over write the default.xbe in there. If you can't transfer as, transfer it as is. Rename the default.xbe that is currently in the E:\dashboard folder to evox.xbe and then rename the SHORTCUT by TEAM XBMC.xbe to default.xbe. Works either way.
Create a text file using notepad or another text editor that has one line.
Save it as default.cfg
FTP it to the Xbox in the E:\dashboard folder.
Reboot the Xbox and you will have XBMC as your dash.