I know this is old, but this is how I fixed it: the archive has the esp/esm files together with folder named "data". The esp/esm files go into the Fallout 3\data folder, but the CONTENTS of the Data folder go into the Fallout 3\data folder as well. So, if you have a data folder in your data folder, move the sub-folders up one level.
Huge Explimation marks. (8 comments)
nvm i fixed it
What ever mod you installed, you didn't properly install the meshes, which will cause the red box/exclamation
A more Clear Readme would have helped alot. >.>