To get back to Captive Portal you don’t have to reboot device.
We don’t know the reason of crashes, but for sure we found the way to fix it. Many users reported that this solution worked.
To fix that you need to restore device firmware using iTunes. Follow those instructions.
How to restore firmware via iTunes?
For now there is possibility to use backward/forward buttons in Captive Portal only. As soon as we find the way to add it in other methods, an update will be released immediately.