The EPG should open with the channel you are watching highlighted, if your guide is always starting on 400 are you sure someone hasn't already set a profile, the shared profile is the default profile. If this isn't the case and you want to set it back to "normal" then maybe a factory reset of the box will work.
Someone did say they changed their Guide to start at the top but I can't confirm that this will work, see message 4 on this thread