I upgraded to 1.1.3 (replaced the old script, run the upgrade)
Then I changed some of the default values in options > image display, for example I changed image and thumb quality to 100 and so on.
I refreshed the database and pre-cached the images.
After that all the images in the cache are gone for good! No matter how many times I hit CTRL+F5 the images are never saved.

I upgraded to the latest nightly build but the problem remains. The cache is always empty.

Are the images showing up in your album? You can check the permissions on your cache folder. They should be 777 (everyone read, write, execute).

Note: Ctrl-F5 has noting to do with the zenphoto cache. There is a link on the admin page (and one for individual albums) that refershes the zenphoto cache.

No, nothing in albums, nothing in subalbums, nothing in image.php.
I get an image only when I click on full image and the permissions on the cache folder are set to 777.

Can we see your site? It's always easier to diagnose if we can see a live site. Thanks.

Sure. Link.

Have you tried turning the mod rewrite option off in admin/options/gallery configuration?

Bingo! Thanks a lot.
Do you know what's causing this? I've always had mod_rewrite enabled before and that never gave me a problem.

Something is wrong either in the .htaccess file of in your server's handling of mod_rewrite. Have you run setup.php on the new installation? It does some checks on the .htaccess file.

I run upgrade.php and setup.php as well.
Btw, is setup.php supposed to look like this? It says the user has insufficient rights but select, insert, update, delete are all granted.

The setup "error" is maybe ok. Setup is trying to check rites on the database. It is being confused by something. Does the database name in the second line match your album database name?

If the name does not match, then it looks like zenphoto does not have full permissions on your albums database. Setup normally flaggs the line that matches the database with an * (at least with the nightly build, not sure when that was introduced.)

You mean this line?
http://i25.tinypic.com/2eed3co.jpg

If it is that one, then I don't think so.
The name of my db is something like xxxx_photos and, I don't know if it should be there, but there's an extra \ before the underscore up there.

Yes, that line. Well, that slash is the problem. Setup is not matching up the db table in the report with the one that you are using for zenphoto. It isn't actually causing you any problems, apparently, so you can probably ignore it. Or you can ask your ISP why the name in the report has the slash.

Ok, turns out the slash wasn't the problem. I made a test database and run a fresh installation of zp, the slash was there but everything was ok.

So I made a backup of everything, deleted the old database and the user, made new ones, upgraded to the last nightly build and re-uploaded everything.
I still don't know what wasn't working but it's fixed now. Yay!
I'm marking this topic as resolved.