Cannot upload images (create directory in image folder)

Hey, folks. I have a client using WP 3.5 in a hosted linux environment with Web Shell 4.4.3 who told me they were suddenly unable to upload images as of December 2012. I took over for them this week. They were back a couple of versions, so I’ve upgraded them, without issue. The rest of the site, including all previously uploaded images, still works fine (before and after the upgrade). I know my way around WP a bit, but am definitely far from an expert.

Details: the original setup was storing images in
riverstoneschool.org/blog/wp-content/uploads/
and “organize my images into month and year based folders” is turned on.

This worked (and works) for all the previous images. However, it failed when uploading new images. They appeared to be uploading _somewhere_, because in the media editor they show up when editing the actual images, but thumbnails and links within the blog appear as broken-image-icons. When I check in the file manager for the website, I can see that the 2013 and prior years folders are there. However 2013 folder has a different owner and group (rischool:rischool) than all the prior years (httpd:httpd). I don’t have a way to change this via my cpanel and don’t have terminal/shell access on the account.

I’m not sure what the original reason for that goofy image location was, so I decided to switch back to just plain wp-content/uploads. Site still works fine and images on the site are loading fine. But now when I attempt to upload a new image into a post I receive an error in the Media editor:
“Unable to create directory wp-content/uploads/2013/01. Is its parent directory writable by the server?”

I get the same error when attempting the upload directly in the media section rather than via the media editor within a post. I double-checked the wp-content directory and it’s owned by rischool:rischool and is 777, or reading/writable/executable by user, group, and other (little concerned about that, but bigger issues at the moment). So it should be open for the server to create anything needed. Uploads has similar 777 permissions and is owned by rischool:httpd, so I just don’t see where the issue lies.

I have disabled both plug-ins we were using (select all – Disable), but in vain. If you’d like to review the site itself, it is at http://www.riverstoneschool.org/blog (a sub-set of the http://www.riverstoneschool.org site itself).

All suggestions gratefully appreciated.