Go to the "Arrival" album. Select the whole album, the press "Tag" (or hit Alt-Enter). You should see the tags in the left pane.
I'll bet dollars to donuts that something is amiss with the Artist or Album Artist tag. Something as simple as having a SPACE after the artist name can make it appear to be a different artist. If you hover over the Artist or Album Artist field, it will underline the name, so you can see if it has leading or trailing spaces.
One other idea with ABBA specifically is that they sometimes their name is printed with the first B backwards. If one of your albums has the Artist field set to ABBA with a backwards B character that would definitely do it. Not likely, but....
Good luck and feel free to take some screen shots and post them here so we can figure out this mystery for you!
Brian.