It seems that sometimes when Gwibber crashes (for me it was https://bugs.launchpad.net/gwibber/+bug/542748) it messes up a gconf key. Particularly the one in apps/gwibber/preferences/streams. Mine was set to [{}]. I changed that to [] and Gwibber launched but no streams were visible. I hit the Gwibber menu button and then New Stream and Gwibber works for me again. Now the value in gconf for me is: [{"account": null, "transient": false, "stream": "messages"}].
It seems that sometimes when Gwibber crashes (for me it was https:/ /bugs.launchpad .net/gwibber/ +bug/542748) it messes up a gconf key. Particularly the one in apps/gwibber/ preferences/ streams. Mine was set to [{}]. I changed that to [] and Gwibber launched but no streams were visible. I hit the Gwibber menu button and then New Stream and Gwibber works for me again. Now the value in gconf for me is: [{"account": null, "transient": false, "stream": "messages"}].
I hope this helps get the bug fixed.