New images no longer displaying

I’ve used the admin tool to upload other images just fine. A couple days ago I moved our site off its original Windows server and onto a Linux server, to accommodate a bunch of plug-ins that weren’t playing nicely. I don’t know if this move is coincidental to my current image problem or if it’s the cause of it, but today when I went to upload some new images, they no longer appear. The admin tool works fine, lets me assign metadata, actually uploads the file and everything…but there is no actual IMAGE anymore, even in the admin tool. It shows the file but not the picture, both in the admin tool and in the page where the file is attached.

http://doublecircleranch.com/wordpress/?page_id=36 is an example.

All the images I’d uploaded previously are still just fine. I tried circumventing the admin tool and uploading the image directly to the directory, but ran into the same problem.

?????

Is this somehow related to my switching to Linux? Whatever’s going on, how do I fix it?