Redmine

I've just tested on demo.redmine.org and it does work fine.
http://demo.redmine.org/issues/736

I see that demo.redmine.org is running 1.3.0.devel.8684.
My setup is running 1.3.0.

About your application's environment
Ruby version              1.8.7 (x86_64-linux)
RubyGems version          1.4.2
Rack version              1.1
Rails version             2.3.14
Active Record version     2.3.14
Active Resource version   2.3.14
Action Mailer version     2.3.14
Active Support version    2.3.14
Edge Rails revision       unknown
Application root          /var/www/redmine
Environment               production
Database adapter          mysql
Database schema version   20110902000000

About your Redmine plugins
Redmine Better Gantt Chart plugin                0.6.0
Redmine Wiki Gchart LaTeX-style Formula plugin   0.0.4
Stuff To Do Plugin                               0.4.0
Redmine XML Import plugin                        0.0.1

Just had the same problem with 1.3.1.

I was not able to open the ticket until due_date was changed. This due_date was set automatically by Redmine when updating child issues.

mysql> select * from issues where id = 19\G
*************************** 1. row ***************************
              id: 19
      tracker_id: 2
      project_id: 2
         subject: xxxxxxx
     description: yyyyyyy
        due_date: 5000-01-01
     category_id: 6
       status_id: 1
  assigned_to_id: NULL
     priority_id: 4
fixed_version_id: NULL
       author_id: 3
    lock_version: 13
      created_on: 2012-01-19 13:00:40
      updated_on: 2012-03-21 16:11:50
      start_date: 2012-02-07
      done_ratio: 50
 estimated_hours: NULL
       parent_id: NULL
         root_id: 19
             lft: 1
             rgt: 14
      is_private: 0
1 row in set (0.00 sec)

mysql> update issues set due_date = "2012-04-15" where id = 19;
Query OK, 1 row affected (0.18 sec)
Rows matched: 1  Changed: 1  Warnings: 0