cocos2d: Warning: File not found: particleTexture.png

Question

I have only a line to load particle.png, and the texture is embedded in it.
Sometimes the texture is seen and somethimes it does not appear.
I noticed I get a warning message:

cocos2d: Warning: File not found: particleTexture.png

My just code to load plist particle is this :

CCParticleSystemQuad emitter=[CCParticleSystemQuad particleWithFile:@"rain.plist"];

This is interesting:
Sometimes the texture is seen: sometimes it is not, and instead of the texture I see gradient balls.