When you're updating Creately for Confluence plugin through the Universal Plugin Manager (UPM) or by uploading the plugin manually you might receive an error message "An unexpected error occurred. Please refer to the logs for more information." in the UPM interface and the update will fail.
If this happens it be that the issue is being caused by a configuration variable within your MySQL or other database.
It could be that the packet size in MySQL is not sufficient to upload the plugin. You should check the packet size using the details in this article: http://dev.mysql.com/doc/refman/5.0/en/packet-too-large.html you may need to increase it to 25Mb or more and try again.
In case this doesn't work, please send the Confluence tomcat logs from your instances to firstname.lastname@example.org so we can look further in to it.