The wiki article on installing the IonCube loader warns of this:
In reply to:
... you'll now need to download the appropriate Linux (x86 or x86-64) ionCube Loader package onto your DreamHost account from either the main ionCube Download page or directly from here.
You can tell what version of the ionCube loader package for Linux you will need to use by inspecting the first section of the output of the phpinfo.php program you just created, and looking at the "System" description section. For example, consider the following phpinfo() output:
System Linux bugsy 2.6.24.6-p4-modules-peon-grsec #1 SMP Thu May 15 22:08:43 PDT 2008 x86_64
In this example, the "x86_64" following the time stamp information indicates you would need the "x86-64" version of the ioncube loader package.
http://wiki.dreamhost.com/IonCube_Loader
--rlparker
--DreamHost Tech Support