We've had a couple people mention problems exclusively with the iPad. We have not changed anything on there for a very long time. Our only suspicion is that Apple somehow messed up the built-in Mail app, which is what we use to send out emails. For an experiment, you could try "compressing" the file to see if it makes any difference. Setup -> Reports -> Compress Archive and tap on that row to add a "checkmark". See if that gives you a ZIP file.
