Data precision in textures (shadow mapping)

Hi!
I got some problems with setting up my shadow maps.

I’ve created a FrameBuffer Object with the following settings:

  
glGenTextures( 1, &mOGLDynamicTextureID );

glBindTexture( GL_TEXTURE_2D, mOGLDynamicTextureID );

glTexImage2D( GL_TEXTURE_2D, 0, GL_RGBA16, 
		          size, size, 
		          0, GL_RGBA, GL_FLOAT, 0 );

glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR );

glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR );
	
// Create a frame-buffer object
glGenFramebuffersEXT( 1, &mOGLFrameBuffer );

glBindFramebufferEXT( GL_FRAMEBUFFER_EXT, mOGLDynamicTextureID );
		
glFramebufferTexture2DEXT( GL_FRAMEBUFFER_EXT, GL_COLOR_ATTACHMENT0_EXT, GL_TEXTURE_2D, mapID, 0 );