I have a scene file that pops up this mysterious error message several times on opening. What does it mean and how do I get rid of it?

The only file I can find that mentions it, is "poser1SetTemplate" in my Poser3 directory.

It appears to be something similar to "GetStringRes" but for referencing a standard string (in this case a OBJ file) in an alternateGeom block.

If you can figure out what files it should refer to (and they still exist) you could replace the occurences with an "objFile" line (as used in geometry switching).

The figure that causes this is either Jessi or a Jessi clothing item.

Very odd indeed, as my ProPack EXE has the "ActorResIndex not supported any more" message in it.
Poser 3 seems to be the last version that supported it.
Best guess is that it was used for the Poser 1 or 2 hand geometry switching.

If the PZ3 isn't too big, you should be able to locate which item is causing the trouble, by opening the file in a text editor.
Search string would be "actResIndex".

If the file does load, the best strategy would be to remove one item, save to another file, repeat until you don't get the message.
You can then remove everything else from the original. At this point you should be able to use an editor to inspect the file.

I have this problem also and tracked mine down to Jessie's sci-fi suit from Xurge: http://www.xurge3d.com/poser_6_jessi?b=1

Yep - that's it. Were you able to correct it?