I'm a tenacious little b*tch. I don't give up easily. Guess what I did? I found a way around it.
1. Look for both cds in the freedb website.
2. Choose one of them.
3. Add that cd the way you would add any other cd.
4. For the remaining cd, find it's freedb page and click on the link next to "ids:"
5. Save the webpage that you are taken to.
6. Go into the program, click on database menu, import and export, import from local free database.
7. Enter the location of the saved freedb webpage on your harddisk and hey presto . . . it should work (and you aren't left with a black cd icon).

Well it did for me, for that cd.

Would that work for others?

Before I forget, thank you for taking the time to answer my question. I now know why it wasn't working. Trust me to have two cds with the same freedb id!!! This world loves doing things like that to me.

I'm going to bed now. It's 6.10am. I'm still hyper from the Biffy Clyro gig I went to last night.