Novell Data Synchronizer Mobility Pack
After you sync a posted appointment from a GroupWise calendar on iPhone you can only Accept / Decline it. There is no Edit option available. A regular appointment, however, can be edited.
This happens only on iPhone 4 with upgraded iOS6.x.
It works fine on iPhone 5 with the same version of iOS.
This fix has been included in the 1.2.5 build 299 release.