Okie dokie then.
There isn't much you can both try to get back on. And from the 3 things that are usually tried, the first 2 are rarely successful. But, if there's a chance, it's worth the try.
1st- Go to the
Usual Place and download an xbox program called Enigmah video mode switcher. It might be under a different name, but I believe is the only thing under the video mode editing section.
Once you have that in your xbox, run the xbe (you will have to unzip/unrar it first) and switch from whatever mode you are, to the oposite mode, then back to your original mode, and reboot. Try to connect and make sure your chip/softmod is deactivated.
2nd- If you've been using ConfigMagic Final lately, to check your eeprom config or to modify it. It should have created a backup of your eeprom on the root directory of one of your drives, or if you bought it, try the original file. Try reflashing that eeprom backup with a different program (Except EEPROMER, unless you have a 1.0 xbox, and I would avoid that as well). And also, relocking it with other than ConfigMagic. Again, I want to make clear, I have nothing against ConfigMagic Final. I've tried and it did the job nicely. But in some cases, wich are rarely seen, it doesn't lock the HDD correctly. And that's why the locking with a different proggy suggestion.
You can also get an eeprom Backup from evox with the backup utility.
Make sure the eeprom is alright, you can check it with a program called LiveInfo from TEAMASSEMBLY, the same makers of ConfigMagic. Make sure it's the same version your xbox is, and if not, convert it. Note that for 1.0's you can only use original 1.0's. And for 1.6's, you can only use original eeproms from 1.6's box.
3rd- Get/Buy a new eeprom and try with it.
Good luck both of you, hope I made sense and that you can get this working the cheap way
EDIT: ALWAYS KEEP AN UNTOUCHED BACKUP OF YOUR ORIGINAL EEPROM BEFORE YOU MESS WITH IT 
