Hello Jeff
I have tested this plunging on BlogLines.co.za MultiSite + Multi DB + 100K sites and i can confirm that the plunging brakes the crop image function in WordPress 3.5
My test was as follows
1) Upload a new image
2) Click Edit
3) Click Edit again below the image
Now this is the step that don’t work any more
4) Now with your mouse drag over the part your need and then press the crop burton and click save.
Just after step 3 I get this err
Could not load the preview image. Please reload the page and try again.
I hope there helps you to dig deeper ??
Ps how do we know that the plugin is working is there any log we can have a look at.
If you need to drop me a line for some testing on my server then please do https://en.gravatar.com/bloglinessouthafrica
@drew_13 I have just posted in your tread as i did not want to start a new tread if you want i will move my comment.