When I drag a subtask to a column with several states, some states might be unreachable in some cases.
As I might be hard to understand trying to explain it, here are steps to reproduce :

case 1 :

1. configure a board with a column containing many status (on my jira, I have a column with 4 status)
2. add a single subtask to a task
3. move the created task to the multi-state column by dragging it from a point close to the top or the subtask's rectangle.

Result :

• The bottom status are displayed, but not reachable

case 2 :

1. reproduce steps 1 and 2 of case 1
2. move the created task to the multi-state column by dragging it from a point close to the bottom or the subtask's rectangle

Result :

• The top status are displayed, but not reachable

I stay available if you need some more details to reproduce it.

Additional Information

Screencast with JIRA 5.1.6 & GreenHopper 6.1.3.1 - http://screencast.com/t/MGz62eMc
Screencast with JIRA 5.2.11 & GreenHopper 6.2.1 - http://screencast.com/t/6pVcKmCi