I hate to chime in on an older post but I it still very relevent to me. I posted a complaint about this exact problem about a year ago (I know others had as well), and was told that PHP now only supports the form index and not the id... or something of that nature, so that is why the index has to be used from now on. The problem is that when dealing with forms when there is an include file above with another form, or when adding new forms above existing ones, the WA Validation gets confused. This has been one of the banes of my existence for the last year... whenever I have to update certain site with Validation Toolkit... I shudder because it has become so aggravating under these circumstances.
