"setgroups() failed..." error for non-root

I have a primary exim binary (called "exim") that I compiled just fine and
that works just fine. However, when I tried today to compile a second
exim binary (called "exim3") for mailing list distribution pruposes, I ran
into trouble. When I run the "exim3" binary as anyone except root, the
process dies with a "setgroups() failed: Operation not permitted" error.
The error seems odd, since I thought setgroups() would only be called when
the binary was run as root. Have I screwed up somewhere in my Makefile or
config file, do you think? What excepts would be relivant to provide?

Thanks.

-Chris