Care to share that portion of your code? I suspect that you're not using double-buffering and are clearing the screen at an inappropriate time.

You are cleaning the buffer every loop. Are you also writting the text every loop?

No, when i enter in a state, a text must be written on the screen and keep there. So, i just write this in that moment, not every loop.

Now it's better, the text still flicking but i can see this for more time. Maybe the problem is i'm not wrtting the text every loop like ReyBrujo asked.

/*Coloca o buufer na tela*/
blit(buffer,screen,0,0,0,0,640,480);

/*Linmpa o buffer*/
clear(buffer);

Switch these two things so it clears the buffer first and then blits.

No, the only thing is the call textoutput inside.

Ok, here it goes:

When i call the warrior->start(); the start() function calls the Sleeping::entry().
Following it calls the execute() and later the exit(), so it goes to the next state. Each state is like this code.

[EDIT] Sorry guys, the name of some functions are in my language (Portuguese).

He should do ALL the drawing at once, and not do any in the logic loop.

Have you tried writing the text every time? Something like:

void double_buffering()
{
        ...
        if (player->state == SLEEPING)
            textout(buffer,font,"I'm very tired, i need to sleep",0,0,makecol(255,255,255));
  blit(buffer,screen,0,0,0,0,640,480);
  clear(buffer);
        ...
}

That's how you have to do it. You (in most cases) cannot draw in your logic loop like that without flickering.

[edit]
If you lock drawing AND logic to the timer you could but there's no point in doing that.

Make a message system like that then... you set the message up and then have a manager which draws them when its time to draw.

C tends to call it NULL.

Anyway: Separate logic from drawing!
Put all the logic into a logic_update() function, and the drawing into another function. Call the appropriate one in the main loop. The drawing procedure is:
1. Clear back buffer
2. Draw scene (background first, then objects, then overlays)
3. Flip buffers, or blit back buffer to screen

The logic function must never touch any graphics routines, and must not call any function that does. Ideally, the logic function has no idea where to draw to (which is why the back buffer should not be a global var, but rather be maintained by the main loop or a dedicated module, and only passed to the drawing code).

The drawing function must not change any state of the game logic. In C++, an object's draw() function should be const. Regard the game logic as read-only in the drawing function.