Right for the last 3 hours I've been trying to find a solution to this, I am building a DOD map, and all is going well, until I try to add a sprite.
I insert the entity select the sprite and the render options, and click ok, the entity box is visible in 2d views, but the sprite is not visable in 3d mode. I've tried various sprites and it appears that only sprites with more than one frame are disappearing. I've set up Hammer 3.5 for DOD accordingly, and am using an up to date FDG.

Any Suggestions

Note that when I Start a new map with the DOD settings and create the env_sprite entity it is visible and in full glory, i go to copy this to the map I'm working on and it becomes invisible again