[imp] Newbie installation help

[Rob Brandt]

Hello;

I trying to do a horde/imp installation on my own server in
preperation for a new position I am taking at an organization that
uses an older version.  My own server runs YellowDogLinux, apache,
php 4.2.2, mysql, postfix and courier-imap.  I have installed the
latest stable releases from the noarch RPMs of both Horde and IMP.
 I've run the mysql_create.sql script and the database is created.

Frankly I'm lost.  I have heard horror stories about trying to get
it installed, and I'm beginning to see why.  I'm sure it's rather
obvious when you know what you're doing, but I don't know how
Horde works and have no idea what to do with the configuration
files.  I've made an attempt at setting the preferences in
horde.php at their simplest options but when I try to access Horde
at http://myserver.com/horde/ I get an error message as:

Fatal error:  Call to undefined function:  _() in
/var/www/html/horde/templates/index/notconfigured.inc on line 4

Which isn't very descriptive.

Where do I go from here?

Rob