I've just installed weinre on my Mac OS 10.8 system using npm (I have version 2.0.0-pre-HA5N9T49). Everything fires up OK, and it appears that the debug target connects fine, but no targets ever show up in the client UI. If I turn on debug, I get output that makes me think that the issue isn't the target:
2013-03-25T19:10:04.564Z weinre: POST /t-1 [request]
2013-03-25T19:10:04.564Z weinre: NetworkNotify.didReceiveResponse([6,1364238604.562,"XHR",{"mimeType":"application/j...)
2013-03-25T19:10:05.004Z weinre: --------------------------------------------------
2013-03-25T19:10:05.004Z weinre: POST /t-1 [request]
2013-03-25T19:10:05.004Z weinre: NetworkNotify.setInitialContent([6,"[{\"id\":1000,\"commuteDistance\":0.0,\"unit\"...)
2013-03-25T19:10:05.004Z weinre: NetworkNotify.didFinishLoading([6,1364238604.563,null])
2013-03-25T19:10:21.317Z weinre: --------------------------------------------------
2013-03-25T19:10:21.317Z weinre: POST / [request]
2013-03-25T19:10:21.317Z weinre: {"id":"anonymous"}
2013-03-25T19:10:21.318Z weinre: --------------------------------------------------
2013-03-25T19:10:21.318Z weinre: POST / 200 [response]
2013-03-25T19:10:21.318Z weinre: {"channel":"c-2","id":"anonymous"}
2013-03-25T19:10:21.359Z weinre: --------------------------------------------------
2013-03-25T19:10:21.359Z weinre: POST /c-2 [request]
2013-03-25T19:10:21.359Z weinre: Network.cachedResources(["c-2::1"])
2013-03-25T19:10:21.370Z weinre: --------------------------------------------------
2013-03-25T19:10:21.370Z weinre: POST /c-2 [request]
2013-03-25T19:10:21.370Z weinre: Inspector.hideDOMNodeHighlight([null])
2013-03-25T19:10:21.371Z weinre: Runtime.releaseWrapperObjectGroup([0,"watch-group",null])
2013-03-25T19:10:21.371Z weinre: Runtime.releaseWrapperObjectGroup([0,"watch-group",null])
2013-03-25T19:10:21.371Z weinre: Inspector.removeAllScriptsToEvaluateOnLoad([null])
2013-03-25T19:10:21.371Z weinre: WeinreClientCommands.getExtensions(["c-2::2"])
2013-03-25T19:10:21.371Z weinre: Inspector.populateScriptObjects(["c-2::3"])
2013-03-25T19:10:21.371Z weinre: Console.setConsoleMessagesEnabled([true,null])
2013-03-25T19:10:21.371Z weinre: CSS.getSupportedCSSProperties(["c-2::4"])
2013-03-25T19:10:21.371Z weinre: WeinreClientCommands.registerClient(["c-2::5"])
but the targets section stubbornly remains empty. Any ideas?