In the jenkins setup wizard, on the "Getting Started \ Customise Jenkins" screen where it asks you to either "Install suggested plugins" or "Select plugins to install", if jenkins is running slowly, eg an NFS filesystem, slow machine, or you are installing remotely over a slow connection, clicking either button gives an error after 10 seconds
An error occured
Unable to connect to Jenkins
The reason for this is simple: in static/c9073345/jsbundles/pluginSetupWizard.js, there's a timeout (line 1919 in 2.60.3):
10 seconds isn't long enough on this setup. Changing this to 180s solves the problem (it actually takes roughly 30 seconds for me)
FYI, on my setup, the page /pluginManager/plugins that is timing out takes 18s to actually load once I increase the timeout although I imagine it could be higher than this for others.