I had that issue last week with my bookmarked login page (www2). I went to the VM front page (www) and logged in there no issue.i can get in to the site
seriously. they've emailed me back about half a dozen times now, and it's always ##VIRGIN# dialer code and/or various ways of running the activation.
i've only ever had the one device during my time on virgin(or any sprint), i ported over my number from verizon.
but, as a commentary on how un-robust their system is, this is useful.
I wonder if in your case if you re-activated the old phone with a dummy MDN/MSID you probably wouldn't have had the same problem. Could have been colliding at that level?