Go back through the user profile part of your return 'manually'. By that, i mean, click on each section of the profile details until you find the one where it asked you about giving your info for donor lists. I had this error myself, but was able to file successfully once i found that and responded. It wasn't a question that was asked when you went through the first time.
Edit: I just went back to see specifically where to do this. It's on the page 'Canadian Citizenship' in the MyInfo tab. There are a series of questions there including the one about organ donation.
