[Jeroen]

I'm not doing anything with images or custom images. I have Grid and its required plugins installed exactly how they are released. The only settings I "tampered" with are background video and trailer on and off.

I'm not saying you are, I was referring to badaas's comment. What he meant is how it might be a problem when colorbox is "fed" images which are in the skins media folder. And the default background image is the only candidate for this.

Some possibility, that the groups of channels in the PVR are via PopUp, when the list is large go from one group to another is something long, sorry for my English, I only speak Spanish.

I'm sorry, but I don't really understand what you mean. Maybe you can post screenshots to explain?

i think the same happens with horizontal menu, check it if you want

Should not happen with the vertical menu anymore. Will be fixed in the next version for horizontal menu, cheers.