Problem with WordThumb script. Help?

Okay, I’m running a Multisite. It has several sub-sites (domain mapped with WPMUDEV plugin) that are using themes with the WordThumb (which became TimThumb 2?) script in them. We’re not sure when, but recently the script just stopped working. Bam! Most images are now broken. On a couple of the sites, we just disabled the script (theme had the option) and they were good to go. However, on one, we’ve still got all kinds of image problems.

The site is http://aspenlanding.com/ –you’ll see that even the logo is affected. You can run the script from the address bar like this: http://aspenlanding.com/wp-content/themes/rezo/themify/img.php?src=http://aspenlanding.com/files/2013/01/aspen-landing-web-logo.png as you can see there’s a bunch of errors. Any ideas where I would look to resolve these? Also, any clues about what might’ve changed that would cause them to suddenly start, when they worked fine before?