Posertrust.cfg is not a firewall thing. It is a file added by the Poser installer, and is there to tell the Adobe Flash player that the Poser library GUI components are trusted. This let's them do things that a Flash app is usually not allowed to do.

The name of the file is not important, but the contents should be the exact path to the folder that contains LSMGUI.html and LSMGUI.swf.

The library GUI is a flash app and must talk to Poser itself via sockets. This is local loopback and does not involve connecting to the network. But, the OS still considers it network communication (never understood why but I digress) and sometimes firewalls prevent it.

These are two reasons the GUI failed in the past, so we check these. I think there is something larger at work here, though. I have a laptop at home that won't run any Flash files, not just Poser, even though I have the latest Adobe Flash player installed on it.

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Renderosity forum reply notifications are wonky. If I read a follow-up in a thread, but I don't myself reply, then notifications no longer happen AT ALL on that thread. So if I seem to be ignoring a question, that's why. (Updated September 23, 2019)