results of attempting to chat while sitting on a (non phantom) prim:

1) avatar sit position raises into the air (avatar is now sitting above the prim)

2) "typing (while sitting)" animation plays

3) "typing while sitting" animation gets stuck and continues to play even after chat is closed

4) region console throws an exception:

ERROR [ ]: System.NullReferenceException: Object reference not set to an instance of an object
  at OpenSim.Region.Environment.Scenes.ScenePresence.UpdateMovementAnimations (Boolean update_movementflag) [0x00000]
  at OpenSim.Region.Environment.Scenes.ScenePresence.setTyping (Boolean typing) [0x00000]
  at OpenSim.Region.Environment.Modules.ChatModule.SimChat (System.Object sender, OpenSim.Framework.ChatFromViewerArgs e) [0x00000]
  at (wrapper delegate-invoke) System.MulticastDelegate:invoke_void_object_ChatFromViewerArgs (object,OpenSim.Framework.ChatFromViewerArgs)
  at (wrapper delegate-invoke) System.MulticastDelegate:invoke_void_object_ChatFromViewerArgs (object,OpenSim.Framework.ChatFromViewerArgs)
  at OpenSim.Region.ClientStack.ClientView.ProcessInPacket (libsecondlife.Packets.Packet Pack) [0x00000]
  at OpenSim.Region.ClientStack.ClientView.ClientLoop () [0x00000]
  at OpenSim.Region.ClientStack.ClientView.AuthUser () [0x00000]
  at (wrapper delegate-invoke) System.MulticastDelegate:invoke_void ()


5) STAND UP no longer functions. avatar is stuck typing while sitting.