I had originally tried to update mozilla-firefox in OpenBSD 3.9 from
version 1.5.0.5 to version 1.5.0.7 in interactive mode. It gave
ambiguous versions, I chose the latest aforementioned, and it failed
to install due to lib incongruities. So, ran pkg_delete on 1.5.0.5 and
it failed to remove some of the mozilla directories. I did it manually
and then tried to install version 1.5.0.7 and ran into the problems below.
Running pkg_delete .libs-mozilla-fireofox-1.5.0.5 did the trick.

Script started on Fri Nov 10 16:53:47 2006
# pkg_add mozilla-firefor x-1.5.0.7.tgz
Can't install mozilla-firefox-1.5.0.7 because of conflicts
(.libs-mozilla-firefox-1.5.0.5)
Error from ftp://ftp.openbsd.org/pub/OpenBSD/3.9/packages/i386/:
ftp: -: short write
421 Service not available, remote server has closed connection.
/usr/sbin/pkg_add: mozilla-firefox-1.5.0.7.tgz:Fatal error
# ^D

Script done on Fri Nov 10 16:54:43 2006

Here's the link where I read up on how to fix this problem:

http://archives.neohapsis.com/archives/openbsd/2006-05/3003.html