The Cable tools use auto-classing. Take a look at the classes generated by the tools (prefixed with CABLE) and hopefully you will see that some of the classes generated by the tool have their fill set to black.
It's because you are using the title block on a design layer. If you insert it on a sheet layer, then all will be well. It seems that if you have design layers set to a scale other than 1:1 the title block will remain fixed at the scale it was drawn at. Very counter intuitive I agree. The fix, if you want to use a title block on a design layer drawn at a scale other than 1:1 is to edit the title block and scale accordingly.