Yep, ProPhoto. It wasn’t a compatibility issue. I upgraded to WP3.6 after experiencing the problem thinking it might help, but it didn’t. BUT I did get a solution I thought I’d share in case others have a similar issue in the future.
This is from ProPhoto’s tech support:
Please try this trick:
In ProPhoto, visit this screen:
“ProPhoto” > “Customize” > “Site Settings” > “Misc.” > “Image downsizing”
and click the “Delete modified images” button you see there.
This will remove all *copies* (not originals) that ProPhoto has created to fit your blog – images that needed to be downsized to fit the main width, images that were downsized for mobile devices, images used for Grid thumbnails, etc.
This will clear up some space on your server, and ProPhoto will simply recreate any downsized images as it needs so things will work just fine.
