Hello I just recently instaleld Zenphoto and I did a a bulk upload to an album. Some of images had its thumbs created ok others did not.

Here is a link.
http://www.rantingcanuck.com/zenphoto/

Any suggestions on how I resolve this?

At the top of your zp-config.php file, you'll see a line that says:
define("DEBUG", false);
Change it to:
define("DEBUG", true);

See if that gives you anymore clues as to what's going on.

I just did that and I am not getting errors at all. I just uploaded a new batch of photo's and I am getting the same issue.

http://www.rantingcanuck.com/zenphoto/

Have you made sure that you've given your albums folder and your cache folder write permissions?

chmod 777 albums/ cache/

I just confirmed the settings and both albums and cache folders have write permissions.

I think I figured out your problem. It seems as if you're getting thumbnails of only the "smaller" sized pictures. I'm guessing that php's 'memory_limit' on your server is set to a low number. You can verify this by doing a phpinfo() and looking at 'memory_limit' which is listed under PHP Core Configuration.

If you have access to your php.ini file, try setting it to 64M or higher. If not, ask your host to increase the 'memory_limit'. If they don't want to do it, then I guess you'll have to resize some of those pictures yourself.

It does not look like a memory problem.

Just look at images paths:
FAILED: http://www.rantingcanuck.com/zenphoto/darryl-and-annette-s-wedding/image/595/IMG_3393.JPG
OK: http://www.rantingcanuck.com/zenphoto/cache/darryl-and-annette-s-wedding/IMG_3557.JPG_595.jpg

I would remove this album. Clean cache. Clean database
And re-upload all images in order the database to be filled once again correctly...

Did you do a change on your server? A zenphoto upgrade ? safe_mode going on suddenly?

Look at this: http://www.rantingcanuck.com/zenphoto/darryl-and-annette-s-wedding/image/595/IMG_3393.JPG_595.jpg

-) It's quite better, except that the thumbnail does not exist

I have exactly the same problem.
Take a look at my gallery: http://www.johnny.nu/zenphoto/

I did a clean install of zenphoto and activate the debugger without any errors.
Don't know what to do.