There are two solutions on how to resolve this issue:
We have distributed a new version of the Symbian Anna 1/2 installation package, that you can easily download by using the software update application on your phone (visible under Menu > Applications > SW Update for Nokia N8-00 and E7-00 or Menu > Applications > Tools > SW Update for Nokia C6-01 and C7-00).
Note: If you have used the SW Update application in the last 24 hours, please reset the cache by changing the date of your phone to a date 4 weeks from now.
Even if you got the message that the update failed, most of the content did get installed nevertheless. The only applications missing are the Quickoffice and Adobe Reader (pdf).