I'm having the same problem described here and posted it a few days ago.
I'm quite sure it is a permissions problem, as I can't upload files or create albums until i manually recreated the image-gallery subfolders structure (/pagename, /pagename/_resampled, /pagename/Default-Album and /pagename/Default-Album/_resampled) with my own shell account.
Are you using a earlier version that doesn't have these problems, as I might think about downgrading the system so creating albums and uploading images works?
The strange thing is that the ImageGalleryPage folder gets created in assets/image-gallery with www-data as owner, but the script fails when it tries to create the Default-Album folder in it (with, as far as I can see) the same owner.
This is the error i recieve:
Error: Uncaught Exception: Cannot move /var/www/vhosts/mysite/httpdocs/assets/image-gallery/New-ProjectPage-2/ to /var/www/vhosts/mysite/httpdocs/assets/image-gallery/New-ProjectPage/
At line 409 in /var/www/vhosts/mysite/httpdocs/sapphire/filesystem/File.php
There's no New-ProjectPage-2 folder, nor a New-ProjectPage folder.
But there is a new-projectpage folder (lower case)
I am running SS v2.4.0 and already have "modules-dataobject_manager-r395" and "modules-swfupload-r375" running.
I just installed the "modules-image_gallery-r493" image gallery. Then ran dev/build.
When I create a new ImageGalleryPage, the new node appears in the menu tree, but on the main part of the screen all that prints is, "Fatal error: Class 'ImageUploadField' not found in [myPath]\SilverStripe\image_gallery\code\ImageGalleryAlbum.php on line 27".
What do I do?
(PS. One thing I did notice is that, on this page, http://doc.silverstripe.org/modules:image_gallery, you mention that the image directories that get created will be called, ".../MyImageGalleryPage", whereas the directories that actually get created are called, ".../NewImageGalleryPage". Might this be significant?)
@CHD: Subdomain. Shouldn't make a difference.
Btw, problem is solved now: it really was a permission thing. I needed to make a few more attempts with changing permissions, don't know why it didn't accept the changes first, now it works. That's it! Hooray.
The problem was with filesystem out of sync, but when trying to sync I got "There was an error looking for new files". So I've made it by hand removing all orphaned records in File table (the easiest way is to backup DB and assets filesystem, remove all files and folders from assets and remove almost all files from File table) . Now everything works fine (I'm wondering for how long).
Just as an update to people still having an issue with this, changing the permissions on the 'image-gallery' folder in assets to 777 appears to solve the problem (mine was at 755, like the rest of assets). Not sure why yet, I'm still working on figuring out what the lowest permission level that works it, will update once I know.