Sorry, I meant to include the technical details.
I am using FEFLOW 5.3 on a Windows XP machine with quad processors running at 2.66 GHz, 3.25 GB RAM.
I started using T-mesh. The model domain is regional in scope but I need a relatively fine mesh in the plume so I created a super-mesh with three polygons and four or five point add-ins. The intent was to specify 100,000 elements, then generate the mesh areally by specifying five times the suggested number of elements in the inner polygon, twice the suggested number in the intermediate polygon, and no additional elements in the outer polygon. I am sure that I do not have holes or overlaps in my polygons. The point add-ins are "close" to each other at the scale of the model as a whole, but not so close in terms of the real distance. I tried setting "medium", "low" and "no" refinement around the point add-ins. I don't recall if I tried adjusting the speed and quality control.
When that didn't work, I tried changing the element number distribution from 100,000 to 50,000 to 25,000, etc., and the multipliers for each polygon (2, 1.5, 1, for example). I also tried different supermesh designs and slightly modifying the geometry of the final supermesh and the polygons therein.
Finally, I moved to advancing front and finally got the mesh to generate. It's not pretty and no where near the size of the elements I want in the core area (even with globally refining the mesh, twice), and not refined at the extraction wells, but at least the mesh algorithm finished.
Let me also point out that I would get this error message more than once during the meshing using T-mesh. That is, certain super-elements would fail while others would work. This often resulted in a mesh being generated for certain super-elements and not others.