Uploaded photos not showing up and new albums not writable

I recently updated my Gallery to 3.0.9 (Chartres) and added a new album for photos. I then started adding photos, and 82 of them do show up. But I uploaded a total of 105 images, and I can see via FTP that they do appear in the correct album, and are the right image sizes, in the albums folder, but for some reason the additional 23 images do not show up in the resizes or thumbs folders. I have tried to upload them multiple times, and nothing seems to work.

I even tried deleting those images from the albums folder and re-uploading them. Didn't work. I can't find anything in my settings that limits me to 82 images in a folder now.

So I tried to add a sub-folder in that folder, and it came up saying 'not-writable'. I couldn't see that the folder was created when I looked in the FTP hierarchy. All my permissions and file levels should be correct; I've never had this problem before.

Any help would be appreciated. What information do you need from me? Thanks!