The scrollbar doesn't look like skinned.
It's not skinned, but it is functional. As far as I can find, it's the only one in TC that's not skinned. This make me think it's likely an issue with TC and not Windowblinds.
Ghisler wrote TC in Borland and it's not likely that TC will ever have a native 64 bit app (without a complete rewrite). I'd suggest you look at Dopus. It's a bit expensive, but from time to time you can find it about 40% off at BitsDuJour LINK