I don't know why but suddenly, the trace effect stoped to work.
I can see the trace on the layer preview but not on the Group preview, Out mix preview, or Out.
I try to cancel the antialiasing settings but nothing change.
I'm working on a MacBook Pro '11 quad core i7 2,2 with AMD Radeon HD 6750M 1024 MB as GPU, 8Gb Ram and a SSD drive.
It runs Lion but the problem have begin on snow Leopard