That was very helpful in seeing what you are trying to do and the results you are getting. However, I can't duplicate your problem on my phone. When I follow your steps, I get the expected results rather than what you are seeing.
When you are in the tasks screen, you can hit the menu button and an option to refresh comes up. This basically wipes all the tasks off your phone and reloads them from the server. Have you tried that to see if it makes any difference to your sort problem? My other suggestion would be to contact their tech support and see if they can help.
Sorry I can't be more help here.