I was editing EB files - but they were vanilla files when I started, the GUI ones. I think it is a problem that runs from 1.2 to 1.5 as I've had exactly the same issues with both builds. I'm sure it has to do with editing the GUI tga's themselves though and I initially thought it was the alphas bleeding over into each other or something like that, but now I'm not so sure, and think it could be related to changes made on the RGB layers. I don't know how the game "interprets" these files though, so when I want to make alpha changes, I'm terrified to make them unless it's very tiny. I've worked on these GUI's a lot (doing the eastern, campaignmap-barb, and carthaginian ones for EB, and doing a roman one now), but I still haven't been able to isolate what is causing the problem - though I have been able to get around it every time eventually.