This seems to be a common problem when installing Arch Linux, so I recommend you to read this thread if you are going to install Arch and then OpenOffice, be sure to install also the right fonts.

This command may be useful

pacman -S artwiz-fonts ttf-ms-fonts

openoffice text is nothing but rectangles - Forum: Workstation User
Author: russianwizard
Posted: Sun, 22 Mar 2009 19:32:26 -0400
Last post: Sun, 22 Mar 2009 19:32:26 -0400
[ArchLinux Forums]

Also read the Arch Linux wiki fonts