Even after you delete them all? In that case, delete the html files and then re-run your most recent deck, there should be some sort of error showing up in the nanDECK status window. It might only be on one card, so watch carefully as you build to see if any appear to have errors in them. In the nanDECK folder I believe there is also an error log that you can refer to if you can't find anything amiss; post that here if you can't find anything more specific and I'll take a look.