I would like to inform you that there is a general ASP.NET AJAX Extensions issue, concerning the new iOS 8 and OS X Safari versions. It is affecting sites using ASP.NET 3.5. Basically, the new Safari version is not properly recognized by the AJAX framework as a browser that supports partial rendering, which breaks the AJAX technology. This seems as the most probable reason for the issue described.
In order to fix this issue, you need to edit your browser definition files so that the latest Safari is properly recognized. You can find more detailed information about the issue as well as a workaround for it in the following stackoverflow thread. Note that Microsoft recommends the stackoverflow workaround.
If your issue is the same, this tip would help you solve it.
Check out the Telerik Platform - the only platform that combines a rich set of UI tools with powerful cloud services to develop web, hybrid and native mobile apps.