Vis Decompression Overrun

This error is compiling is a tell-tale sign that you have far too many visleaves in your map. A visleaf, or simply leaf, is generally a brush. This means that you have some very sophisticated brushwork, an enormously large map or just a mixture of the two. Either way take a look back to see if you cannot break up the level or cut back on some of your leaf-use through the use of func_detail geometry.

• This error can occur by placing a large amount of non-detail world geometry in the 3D Skybox.