IB API, reqMktDataEx : error code 200 no security definition has been found for the request

Have you ever encountered this error? I can't figure out for the life of me what is wrong with my IContract. I've made it exactly as it is on the VB.NET sample they included but I'm still getting "error code 200".

I tried using reqMktData() and thankfully it worked! But I am not satisfied. I want to find out what's wrong with my IContract. Here's the inspection before the parameters are passed to reqMktDataEx()

If you've encountered the same error, please share on how you solved it.

EDIT 5 minutes later:

I solved it damn it.

After calling Tws.CreateContract(), do not change IContract.conId ..

why do I need hours to solve such problems... these guys need to work on their documentation.

=======================
oTws.reqMktDataEx(quote.TickerId, quote.contractInfo, quote.GenericTicks, (int)quote.Snapshot);

+	quote
	quote.GenericTicks		string
	quote.Snapshot	0	int?
	quote.TickerId	1	int
-	quote.contractInfo	{System.__ComObject}	TWSLib.IContract {System.__ComObject}
+	[System.__ComObject]	{System.__ComObject}	System.__ComObject
	comboLegs	null	dynamic
	conId	1	int
	currency	USD	string
	exchange	SMART	string
	expiry		string
	includeExpired	0	int
	localSymbol		string
	multiplier		string
	primaryExchange	NASDAQ	string
	right		string
	secId		string
	secIdType		string
	secType	STK	string
	strike	0	double
	symbol	AAPL	string
	underComp	null	dynamic
-	Dynamic View	Expanding the Dynamic View will get the dynamic members for the object
	comboLegs	null
	comboLegsDescrip		System.String
	conId	1	System.Int32
	currency	USD	System.String
	exchange	SMART	System.String
	expiry		System.String
	includeExpired	0	System.Int32
	localSymbol		System.String
	multiplier		System.String
	primaryExchange	NASDAQ	System.String
	right		System.String
	secId		System.String
	secIdType		System.String
	secType	STK	System.String
	strike	0	System.Double
	symbol	AAPL	System.String
	underComp	null

=======================


IBAPI, TWS API, TWSAPI,