When installing the updates to Joomla 3.4.x you may get a popup dialog box message indicating an "Invalid Login". After clicking the OK button the update process will appear as if it is still updating but the progress bar will not move. In this case the update has failed and no change was made to the system.
We found a number of reports of this issue and what we found was that it is most likely a permissions issue on the folder structure where Joomla is installed. By resetting the folder and file permissions so that the web server had complete control of everything, the update competed normally.
Many of our clients have their web sites hosted on Linux servers. To reset the permissions we used the following command at the local server's command prompt.
chown -R {owner}:apache {site's root directory}
chmod -R 777 {site's root directory}
After the installation was completed, we restore tighter control over the web site's installation folders as follows.
chown -R {owner}:apache {site's root directory}
chmod -R 755 {site's root directory}
chmod -R 777 {site's root directory}\tmp
chmod -R 777 {site's root directory}\images
chmod -R 777 {site's root directory}\logs
Once the permissions were updated again we verified that the web site was still working.
We hope that this information is helpful. Please let us know how this has helped you or if you have additional questions. As always Firestone Technical Resources, Inc. is here to help with your computer support issues - "Providing personal service for your impersonal technology."