Seems owners of a Galaxy S II Skyrocket, are getting disappointed today. An Android 2.3.6 update has been rolling out to the phones, but some cannot seem to fully download the file. The update will partially download,  it then fails, and no matter how many times you try it just will not work. Some have even downloaded the whole file and they still get a failed message, and I am sure they have death in their eyes.  Surely AT&T will be rolling out a fix as soon as they can, but check your system updates to see if you have the update in there. Let us know if it is working for you, or you are getting the failed message.
Source: Android Community