You could try that, which we've seen resolve mysterious CB issues in the past, but a problem with that should affect all CB sales, not just some products but not others. If you do this, be sure to use only letters and numbers for your Secret Word, and use your computer's copy-paste functions to make sure it matches at ClickBank's end and ours.
A couple other things I didn't think to mention in my previous reply: make sure you're using your E-junkie Buy Now buttons for ClickBank (rather than any buttons provided by CB itself), and make sure the affected product's price settings match at ClickBank's end and ours.