I can't get to anything at all, I get fatal errors, primarily:

Fatal error: Call to undefined function gettext() in /home/{username}/vd/{website}/zenphoto/zp-core/setup.php on line 21

which comes up when I try to start at the index file, which gives me a page that says:

"Zenphoto error: zp-config.php not found. Perhaps you need to run setup (or migrate your old config.php)"

and the only zp-config file that's there is: zp-config.php.source

Any help would be much appreciated.

Search for gettext in this forum, 3rd hit:
http://www.zenphoto.org/support/search.php?q=gettext

I have same problem. This link can't help me (I don't understood what I must to do) – can someone have easiest way for this problem? Thanks!

So, look like I get help from here: http://www.zenphoto.org/support/topic.php?id=7022#post-41204

To be more direct, you need to open up one of the files, and move some code up a bit:
http://www.zenphoto.org/support/topic.php?id=7022

(for the "Fatal error: Call to undefined function gettext() in /home/{username}/vd/{website}/zenphoto/zp-core/setup.php on line 21" error)

Thanks! ;-)