I needed autoconf 2.61 on FC-6 for something, and updated it from Rawhide locally. However, that resulted in a broken setup without rpm notifying me about it, as autoconf 2.61 appears to require m4 version 1.4.7 or later due to its use of "m4 --debugfile". So the dependency on m4 in autoconf should be made versioned like "Requires: m4 >= 1.4.7". Don't know whether the BuildRequires on m4 should be versioned or not. See also bug 230601 and http://www.gnu.org/software/autoconf/#TOCintroduction
Oops, how did that severity end up as "urgent"? Fixed.
Resolved in autoconf-2.61-10.fc9.