I have an action that I am POSTing to from jquery:
[HttpPost]
public void UpdateGroupName(int groupId, string name)
{
Try without the stringify. I guess MVC is understanding another way of binding besides the request parameter -> action parameter. I guess it's understanding the json posted. JQuery, if you pass just the data object (without stringify) will post each field as a request parameter (at least, I think so). It's easy to try :)