Not sure what happened exactly, but I uninstalled everything in pear (from the horde channel) unregistered the horde channel, cleared cache, and reinstalled everything.
Works fine now!
Strange though, I tried on a Slack 14 VM before I succeded on my local server and it failed too.
I wonder if there;s something Horde doesnt like about Slackware or vice-versa?
Until next time, thanks everybody for the great help!
As usual, slackware rocks!