If you have experienced problems using the Extension Manager Update with prior versions of 1.6, we recommend that you install the 1.6.5 update package by unpacking the archive file. At that point, you will have the fix installed and you can then use the Extension Manager Update for future updates, including 1.7.0. As always, we recommend that you have a current backup of your site before doing any update.
Please note that, starting with this release, we are providing two update packages only. One is for the most recent release (in this case, 1.6.4 to 1.6.5). The other is for the oldest release (in this case, 1.6.0 to 1.6.5). If you are running version 1.6.4, use the 1.6.4 to 1.6.5 update. If you are running any older 1.6 version (1.6.1, 1.6.2, or 1.6.3), simply use the 1.6.0 to 1.6.5 update package. This will work for any of these versions. It may copy some files that don't need to be copied, but this doesn't hurt anything and ensures that all of your Joomla files are current. We hope this will simplify the update process.
The Production Leadership Team's goal is to continue to provide regular, frequent updates to the Joomla community. Learn more about Joomla! developement at the Developer Site.