Hmm. Not sure the cause of the problem in the first place, but I did manage to eliminate the error.
In my case, I tweaked the mesh settings manually (specifying the number of cells in X, Y, Z) to get the mesh to work. Though, There didn't appear to be any specific number of cells that worked...as long as I typed in an even number, it seemed to be OK.
If anyone knows WHY this occurred in the first place, that would be good. It was the first time I have seen this error.
Use the Check Geometry tool.