Forgive me for bringing this back up from a year ago, but this happened to me as well. At work, our guest-net (non-business wireless network) is one which allows any device to log on but then uses an HTTP page to force a username/password before enabling access to the internet. Using my iPhone (iPhone 5, iOS version 6.1.4, the most current version of YNAB on the store as of yesterday), I attempted to start YNAB and it was continually crashing - the app would come up but immediately crash out again. Closing all apps and restarting the phone had no effect. Once the phone was re-started, I realized I was on the network but had never authenticated through the web form; once I did so an attempt to start up YNAB worked perfectly. So as far as I can tell, if the device thinks it is on a network but does not have connectivity through that network, it acts as a crash bug for the app.