The Plugin update installer should follow 302 redirects, not download them.
Attempting to update a plugin via the "Update Center" on the web console appears to succeed, but actually always downloads a "302 redirect" file. Subsequent Hudson re-start then results in plugin failure. (And Hudson offers to discard the configuration)
eg. attempting to update "LavaLampNotifier", the LavaLampNotifier.hpi downloaded is as attached.
Note this happens when we try to update *any* plugin - it is not restricted just to lavaLampNotifier. Can fetch the plugins fine using "wget" :-