I have found and corrected the issue affecting iOS 4.2 users in Dapp. Specifically, any changes to an on/off (boolean) setting were not being applied. The error was caused by a change in iOS 4.2 that now causes the iPhone to wait until the on/off animation is complete before applying the new isOn setting.
The patch has been submitted to Apple and should be available in the next week or so.
Thank you to everyone for your patience in this matter.