It is an iPad problem.
1. Because it's unacceptable when a unit gets looked due to a change in the Exchange password. If you press the cancel button, you may assume your Exchange connection is of course no longer working till the issue is fixed, but not that the unit gets looked forwever. For what purpose it the Cancel button than for canceling the operation. If by design it's just looping, then this is an design error and needs to be fixed.
2. I experienced this problem as well the same way because of the Exchange password change the first time.
But it is now repeating from time to time (without a Password change) and it looks happening, when the iPad connects to a WiFi or network which gives no Internet access. E.g. today it took presumably the WiFi from another house, because my own WiFi seemed to be out of reach. So WiFi connected there, but received no internet access. Because of that, no Exchnage authorisation was possible. Normaly this is not a problem, you dont get prompted to a new password just because of that. Then I tried to access the iPad again when I was out, with no WiFi near and no data connection any where. Same problem..
In the office then, the ipad connected first to the PWLAN instad of mine. Same problem, as no Internet connection was possible. Because of that the Exchange Login was looping despite canceling it and I was unable to access the iPad configuration to force the iPad to connect to my own WiFi. - If this is not an error, what is an error?
Thue to the Tip here of rebooting, I was able to access Conficuration and have the iPad select my WiFi and it all worked WITHOUT that I needed to change my Password, as the Exchange was not changed.
This issue should be corrected by Apple at least to the point, that a Cancel really cancels the process and not leading into a loop, blocking the iPad.