After upgrading to 3.4.0 RTW the task logs are blank. Attached are some images from the task log of the tentacle upgrade after 3.4.0 was installed. As you can see, both the task summary and the task log, set to show All, are blank, but the Raw log has the log information.
This is not only a problem for tasks that ran after the upgrade to 3.4.0, but all older tasks now display like this as well.