Are you using this version of EnhancedStackSplit?
Did Buffalo ever appear skinned? It was changed to have slightly less visible borders around the icons.
Are there no edges to the Buffalo icons visible?, try changing the border colour to red or green to make them more visible.
I am using the version(s) of EnhancedStackSplit that are on the SVN. I update all of my ace2 addons with WAU, so it's always the latest version along with Skinner. If you reread my post a week or two ago, Buffalo worked perfectly fine for me. Ever since the change I haven't been able to see any border. It might have something to do with my using Roth borders for skinner. Roth is already not very visible. Maybe, the change made it look like there was no border at all.
Edit: EnhancedStackSplit works now. I checked the stack split frame. The first time I downloaded EnhancedStackSplit, I had the stack split frame checked. The skin was all messed up, so I unchecked it thinking I needed to uncheck it.
Edit 2: I see a border on Buffalo now when I set it to red. Although, it is very small compared to everything else. I have Buffalo set to 0.9 scale, so maybe the size of Buffalo is creating a problem? Another thing is that when I change the color of my border colors to red buffalo doesn't change. When I change the color of my tooltip border color to red it does change.