It's hard to say for sure what's happening here without looking at the TGD file, so if you can share that to support AT
planetside.co.uk that would be very helpful. In the past I've seen this for a variety of reasons, from use of extreme values such as negative values in cloud or texture settings, or using input shaders to a multiply function that cause high or negative values in downstream shaders, to issues with imported textures and opacity or Unpremultiply settings (this setting is in the Image Map Shader under Colour), to problems with certain AA modes and not using AA bloom (negative lobes) and the renderer producing extreme values that the filter can't deal with. So, like I said, best to provide a TGD if at all possible, and ideally all the objects too so we can reproduce the problem (you can use File->Export Gathered Project), although just the TGD alone would be helpful in itself.
- Oshyan