Ok sorry, I have tried something new: I added again a new IWD file ( there is only weapons ) and it worked!!! (zzz_weapons.iwd)
Then I added a new IWD for menus. There is: ui_mp, images and materials. And again this error... Might be the problem on images with the same file? (zzz_menus.iwd)
I tested it the weapons with images and materials -> worked (zzz_weapons.iwd) + (zzz_menus.iwd)
I tested it the weapons with ui_mp -> worked (zzz_weapons.iwd) + (zzz_ menus.iwd)
I tested it the weapons with images, materials, ui_mp -> didn't worked (zzz_weapons.iwd) + (zzz_menus.iwd) + (zzz_menus.iwd)
I tested zzz_menus.iwd (images, materials, ui_mp) it didn't worked. It's 100% cause of the combination of materials, images (materials and images for the weapon images on the weapon menu) and ui_mp (the menus)
The gamestate is not the problem.
zzz_menu.iwd (images,materials and ui_mp) works on local server (on my PC)