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?

Ok, me too now.

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?)

jf/

@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.

I think I've found solution.

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).