Current version of PaointStop for Zbrush 4 does not work at the moment.
Go to the 3.5r3 and download that version.
It works well with ZBrush 4.
Better still, follow the instructions here:
http://www.zbrushcentral.com/showpost.php?p=718509&postcount=11
New zb4 paintstop works fine here. I just tested it. Its the mac build.
Yes Mac is OK, PC is waiting for the download to be updated. I guess the load on the servers is impacting on this.
marcus,
Thanks again for the outstanding support.