why does claring my URL Stack cause a delay in page reponsiveness ?

Hi ,

I have the following in the server side code. Note the closeURLStack is defined as follows

public Stack CloseURLStack
{
get { return stkCloseURL; }
set { this.stkCloseURL = value; }
}

[WebMethod]
[ScriptMethod()]
public static bool ClearCallStack()
{
   if (userContext != null && userContext.CloseURLStack != null && userContext.CloseURLStack.Count > 0)
      userContext.CloseURLStack.Clear();
     return true;
}

It is called from javascript via the following

function ActionMenuItemClick(e) {
PageMethods.ClearCallStack();
}

It seems that when the user clicks on a menu then there is no responsiveness for about 8 or so seconds and then the page renders . 

If i comment out the PageMethos.ClearacALLsTACK()  it seems to be a bit faster. 

Question is do I need to clear the url stack or is there a better way of doing this ?

Thanks