The easiest way to deal with that situation is to search for the word "Error" on the page. The first instance will be the error message itself, but the second instance will appear directly above the field with the problem. That way you'll be able to see what's giving you trouble. If it happens to be the ISBN field just delete the ISBN; if they are totally accurate the system sometimes throws a fit about them. Yes, a side effect of that error page is that it loses track of which file you were uploading. That can be irritating; I really wish the system would check all that stuff before it took the fiel. That would save a lot of people a lot of time.