What version are you running?
Review Board 3.0 alpha 0 (dev) 
What's the URL of the page containing the problem?
http://demo.reviewboard.org/r/2/diff/1/

What steps will reproduce the problem?

Change revision using the slider


What is the expected output? What do you see instead?
I expect the first FileDiff being selected.
What operating system are you using? What browser?
OSX, Firefox

Please provide any additional information below.
DOM Element #diffs div.diff-highlight is not created after loading FileDiffs from the server. I think that all of #diffs children are removed and only FileDiff elements are created after loading from server.