Problem calling nested web services from javascript

I just started to use VS.NET 2005 and AJAX. Here are what I am trying to do:

In my init funtion that I registered to Sys.Application, I read a value called INSTID from session:

function FCNIInit()
{
     PageMethods.GetValidationKey("VK",OnSucceeded, OnFailed,"VK");
     PageMethods.GetSessionValue("LOGINPATH",OnSucceeded, OnFailed,"LOGINPATH" );
     PageMethods.GetSessionValue("INSTID",OnSucceeded, OnFailed,"INSTID");
}


Then in my pageload funtion I need to pass the above INSTID value to my local web service which in turns call a remote web service:

function pageload()
{
if(INSTID!=="undefined"  )
      {
        MyWS.WS.LMainMenuOther.GetExistingFCNINames(INSTID,OnSuc ...