Fields sticking around when they should be hidden

Here is an example of the problem I am running into. All fields are required.

Option 1
-Problem* (select list)
--General
--Technical

Option 2
-Message* (text box) [appears only when general is selected]
-OS* (select list) [appears only when technical is selected]
--Mac
--Windows
--Other

Option 3
Other OS* (text field) [appears only when Other is selected under OS]

Okay, so if I select TECHNICAL and then when OS appears I select OTHER the OTHER OS text field appears as it should. However if I then change my mind and change the PROBLEM field to GENERAL (without unselecting OTHER) then the OTHER OS text field remains on screen when it should have dissapeared. It does not remain required but for some reason it remains there.

Hope that makes sence.