Parent task translation missing: en, activerecord, errors, models, issue, attributes, parent_issue_id, not_a_valid_parent

Problem
You get the following error in redmine when trying to update a task that has a parent task.

Solution
It seems that for some reason when you add more than one subtask, the lft and rgt id numbers are not created correctly so you cannot update the subtasks.
If the numbers are overlapping (rgt for first subtask 2 and lft for second subtask 2), then there is a problem.
So in order to be able to solve that you will need to change the lft, rgt ids to have subsequent numbers as:
first subtask: lft -> 1 , rgt -> 2
second subtask: lft -> 3, rgt -> 4

passenger ArgumentError (invalid byte sequence in US-ASCII)

Problem
After upgrading your server to use rvm and Ruby 1.9 you get the following error when you are trying to access certain parts of your redmine installation:

passenger ArgumentError (invalid byte sequence in US-ASCII)

Solution
If you follow the instruction posted here, you can add the following to your redmine’s “RAILS_ROOT/config/initializers/string_encodings.rb”:

Encoding.default_external = 'UTF-8'

and restart your application