I don't get this at all. I used Burghound's solution (finding other apple ID's associated with my email) and it worked...BUT, the ONLY reason I had a second apple ID is because when I upgraded my iphone to iOS5, it MADE ME use my email address as my apple ID....yet it still kept my old apple ID, which was not my email address, associated with my email. So I could not verify my new apple ID, because there were now two accounts associated with the same email address.
As Burghound suggested, I just associated a bogus email address with my OLD apple ID, and then associated my real email address with my NEW apple id. But I have no idea if this screwed up any of my purchase history info, I'm sure it did. I don't know why Apple couldn't just map my old account to my new ID, since it was iOS5 that made me change to begin with. Pretty poor.
Also, I couldn't log into the support community with my new ID, just my old one.