Are you doing it with a script or in the dialogue file? Either way, the system is very sensitive.
Initiating a conversation will cancel all animations, no matter what. This is probably hard coded and if so, there's nothing you can do about it. So if you're scripting it, you have fire it again on the first dialogue node.
If you're doing it in the dialogue, you have to apply the animation to every node you want it on, even blank "continue" ones - otherwise the character will stop doing the animation between nodes and start over again in the next node.
Additionally, scripting the animation can have different effects than adding it to the dialogue node. For example, certain dialogue animations, such as Talk_Forceful, force the camera back a bit on angle 1, to prevent clipping. If you script the animation rather than add it to the dialogue node, however, this won't happen.
Last edited by JCarter426; 01-01-2012 at 10:26 PM.