I thought I had posted my solution here recently, but I guess it didn't take.
I tried removing different types of clips from my sequence (HD footage, graphics, stills) and nothing was solved until I removed all the text that I had created within FCPX. Once those were gone I was able to export a clean error-free-upon-import XML file.
I had a bunch of text clips that were just notes to myself. Only two of the clips were meant to be part of the final product and they were easily recreated. I got off easy, I think. Good luck.