For a while now I've been getting the following error (see pic) in the Companion Console on opening a page that has DevComp enabled - it doesn't really affect usage as far as I can see, but I wondered if there is an easy fix or if I'm doing something wrong.
Using DeveloperCompanion 1.0b1rc47, FF Nightly 22.0a1 (2013-03-20), Ubuntu 12.04 (though I think this has been like this since FF 20.0 nightlies)