Weird BibTeX problem

This is puzzling me, and I am hoping my readers might help:

I want to add a reference to this entry:

@article{ref,
author = {First Last and First M. Last, III},
title = {Insert Title Here},
journal = {Int. J. Comput. Sci.},
volume = 1,
number = 1,
year = 2010,
pages = {137--154},
}

and it comes out looking like this (in my .bbl file):

\bibitem{ref}
{\sc Last, F., and First M.~Last, I.}
\newblock Insert Title Here
\newblock {\em Int. J. Comput. Sci 1}, 1 (2010), 137--154

As you can see, there are two problems:

1. The second name is not formatted in the style of the first
2. The second author has been replaced by their grandparent (!) (the III has been replaced by I).
   

This is using the acm.bst style file. I tried using plain.bst, and the problem persists: the second author is listed as III First M. Last.

I tried standard tricks like enclosing the III in braces, placing commas in certain places, removing them etc. No luck.