Regression test errors on x86_64

I'm sure that I'm doing something wrong, but are there any special flags
that I need to pass to configure/make in order to make sure that everything
builds correctly on an AMD64 machine (Quad dual-core Opteron)? Everything
seems to builds fine, however I fail 71 of the regression tests. Looking at
the results it looks like it, many times when the regresssion test expects
and error, my compile doesn't throw one. It happily accepted 'xxx' as a
bool and 'abc' as a char ... is this a known "problem" for x86_64?

Sorry for being so vague, but I don't have the output in front of me (its at
work). What information would be most useful in diagnosing the problems?
(RHEL4 Update 2, PostgreSQL 8.1.3, only options to ./configure are
--with-*).

Thanks
-Mike