OK, I tried 2 years ago and it got rejected immediately.  2 years on I would like to try again and would like to know how.

I have Return to House on Haunted Hill on HD DVD.  it shares the same EAN as 'Message in a Bottle' DVD.  However, I have scanned the disc ID in via my HD DVD drive and  I tried submittingback in 2007 and it got rejected (I believed that you could do this as the disc ID is different).

Can someone please tell me how to get this submitted

I think the biggest reason for rejections is usually because the notes aren't clear enough or don't cover all the changes.
If possible I would create a profile with only a bare minimum of information on it, just to get the profile into the system. Then worry about cast, crew etc. later.
The problem is that if you're creating a new online profile you don't get to choose what data gets submitted, so what I would do is (temporarily) make your profile a manual profile. You do this by going to "Change EAN" and type in "M".
Then create a new, blank profile using the disc ID of your HD DVD. Add title, maybe the cover scans, video info etc. and try submitting that. Make it clear in your notes that you're using the disc ID because the EAN is already in use by another title.
Once that is done (and hopefully accepted), simply delete that profile, go back to the original, and using "Change EAN" again, change it back to the disc ID.

Edit: I just looked at your collection and Spab has it right, you've simply overwritten the Message in a Bottle info locally. As Spab suggests you need to change that profile to use the disc ID instead.