i have also posted this in my Marriage Theory 101 topic
Well from what I have been reading lately it seems you are unfortunately banned again, and this error is a precursor to the actual Modified Hardware error. I guess MS can detect broken marriages as soon as you log in and prevent you from even accessing Live until they add you to the banned list.
My Theory as to why this is happening like this:
I believe MS has instated a sort of Live password as part of the Marriage security measures. Live prompts your xbox for a login of sorts, this login is the same as your EEPROM serial number. It then asks for a password, this password is your HDs lock code or HD serial number. If they do not match what MS has on file on their servers you cannot connect to Live (Live Not Found) and it adds your EEPROM serial to the list of pending bans (same as folks who log in with a hacked bios) If it is a EEPROM they do not have on file they put it on file with the HD code and thus the marriage takes place.
This explains why people who change HDs without changing eeprom cannot access Live at all (since the "password" isnt correct they cant log in) and then only later get th emodified hardware error (after the "classic" ban has been processed)