SendMessage() doesn't work in one project

I tried to use this Watermark it does work correctly on my test project, but it doesn't work in our main project.

How can I debug this? I checked lastwin32error it returns a 0 which I guess is good.

EDIT: It does work in the designer but when I run the project it doesn't.

I created a connect bug report Link I'm still waiting for some response there... I uploaded there the project that makes the problem. If I could upload it here too I'll do it.

EDIT: I found that if I set this 2 check boxes then it'll work... is there a way around it, I don't want to set the 'enable application framework' because it requires a form as the start-up form.

The Windows cue banner, if it's what you're using, has some limitation and requirements.

You cannot set a cue banner on a multiline edit control or on a rich edit control. To use this API, you must provide a manifest specifying Comclt32.dll version 6.0.

See here for the official details: EM_SETCUEBANNER message

EDIT: The Comctl32 issue means in .NET, you mist ensure there is a Application.EnableVisualStyles() line in your program start code, before Application.Run().