OBSD 3.1 i386 su problem: invalid script: /usr/libexec/auth/login_krb4-or-pwd

["Raymond C. Rodgers" <obsd@bbnk.dhs.org>]

I've been in the process this week of updating my firewall to the latest 
patches under OBSD 3.1, and I did something incredibly stupid: I extracted 
a freshly built (but not properly configured) etc31.tgz over my existing 
/etc directory. I knew I did something stupid immediately, and I attempted 
to correct the problem by restoring the directory with a very fortunate and 
recent back-up done earlier this week.

After I finished updating with the other tarballs, and replaced my kernel 
with an updated version (it's custom), I rebooted, and fixed a few minor 
errors and problems. The big problem that I've had since then, is that I'm 
unable to log-in with my usual user account and su. I get the following 
error on the client:

su: invalid script: /usr/libexec/auth/login_krb4-or-pwd

And the following log entries on the server:

Jun 29 09:44:58 alpha su: cannot stat /usr/libexec/auth/login_krb4-or-pwd: 
Permission denied
Jun 29 09:44:58 alpha su: cannot stat /usr/libexec/auth/login_krb4-or-pwd: 
Permission denied
Jun 29 09:44:58 alpha su: /usr/libexec/auth/login_krb4-or-pwd: path not secure
Jun 29 09:44:58 alpha su: /usr/libexec/auth/login_krb4-or-pwd: path not secure

Considering I don't know the first thing about Kerberos, I don't use it. 
(It's on my long list of things to do one day.) So, as you might guess, I'm 
a bit clueless about how to correct this error. I did a search on google 
that turned up some results relating to the sparc port of OpenBSD, but the 
messages (which turned out to be in the mailing list archives) said that 
the problem and fix were only relative to the sparc port.

Could it really be just that my most recent OpenBSD build went awry in the 
login_krb4-or-pwd script? Or am I facing some more devious problem?

Any help appreciated!

Thanks,
Raymond