Hmm, I'll say up front that I don't have a certain answer; re-flashing is going to be difficult if you don't have a working USB port. I have two thoughts:

1) do you have BackupMenu and a recent backup? If you can restore from SD card to a point before you went into offline mode, that might help.

2) this is a long shot, but, you could tell it not to go online, let it boot up fully, and then from a terminal:

/usr/bin/dbus-send --system --type=signal /com/nokia/mce/signal com.nokia.mce.signal.sig_device_mode_ind string:"normal"

Don't know why this is supposed to work if the GUI doesn't, but it's got to be worth a go...