Thanks for the replies folks.
I have tried both the sandbox method and the plug-in.
I can confirm that Jean is correct about the sandbox adding lots of extra edges and unexpected, unwanted faces. It also sometimes fails to make faces depending on the surrounding geometry of the triangulation edges (ie complex shapes). It is however very fast compared to the plug-in.

The makefaces plugin works well but is very slow.
Here is the report it generated after selecting a very small subset (1000 edges) of the large mesh (300000 edges) I have to deal with.

makefaces.rb: Copyright 2004-2006 Burchwood USA.
Version 1.2 May 14,2006.

There were 1000 selected items.

There were 0 non-Edge selected items.
There were 1000 Edges selected.

There were 940 face(s) added.
The process lasted: 1 Minute(s), 5.27200000000001 Second(s).

By my estimate that means my computer is going to be crunching for about 5 1/2 hrs to re-face the entire mesh!
The sandbox method, by way of comparison, took less than 1 sec on the same subset.

Perhaps those ruby script gurus out there who like a challenge can take this one up?!

As a newbie to SU, the forum, and being my first post, please be kind in your replies if I have missed the obvious!

My challenge: I have a very large triangulated mesh (wireframe) consisting only of edges. I need to re-create the faces that should exist within each of the bounding triangle edges. I do not intend to use the line tool to re-draw over thousands of existing edges to re-establish the faces.

My question: Is there a tool or script that has been developed which will automatically re-create all the missing faces from this triangulation mesh?

The details: The (faceless) wireframe was originally derived from a triangulated (faceted) surface of a microstation .dgn file but the conversion to the dwg format (to enable import to SU) only produced edges and not faces. I do not have microstation, so can not export to the .skp format that I know is possible from microstation. I have tried Curviloft from Fredo6 but this does not seem the right tool to use simply to re-create faces from already closed triangles.