[jitter] first shader

hey,
I just subscribed to the jitter list, trying to test a shader but 
something is wrong. I hope it is ok, if I just paste it.
I have to say that this is my first shader, so it could be some very 
basic problem with bindings or jitter communication.
anyway, when I try to load the shader I get:
setting GLSL param: GL Error: Invalid operation
thanks for help,
marius.

---------
<jittershader name="set-alpha">
	<description>Shader to set alpha related to color thresholds</description>
	<param name="image" type="float" default="0" />
	<param name="hithresh" type="vec4" default="0.0 0.0 0.0 0.0" />
	<param name="lothresh" type="vec4" default="0.0 0.0 0.0 0.0" />
	<param name="pass_other" type="vec2" default="0.0 1.0" />
	<language name="glsl" version="1.0">
		<bind param="image" program="fp" />
		<bind param="hithresh" program="fp" />
		<bind param="lothresh" program="fp" />
		<bind param="pass_other" program="fp" />
	
	<program name="vp" type="vertex">
<![CDATA[
// VERTEX SHAADER

varying vec2 texcoord;

void main (void)
{
     gl_Position = ftransform();
     texcoord    = vec2(gl_TextureMatrix[0] * gl_MultiTexCoord0);
}
]]>		
	</program>
	
	<program name="fp" type="fragment">
<![CDATA[
// FRAGMENT SHADER

varying vec2 texcoord;
uniform sampler2DRect image;

uniform vec4 hithresh;    // hi and lo threshold
uniform vec4 lothresh;
uniform vec2 pass_other;

void main()
{
     vec4 A = texture2DRect(image, texcoord);
     A.a = pass_other[0];
     if ((A.r >= hithresh.r) || (A.r <= lothresh.r) || (A.g >= hithresh.g)
		|| (A.g <= lothresh.g) || (A.b >= hithresh.b) || (A.r <= lothresh.b))
	{
		A.a = pass_other[1];
	}
     gl_FragColor = A;

}
]]>		
	</program>		
	</language>
</jittershader>