I'm getting the same message ("... unable to enumerate USB device on port 2"), but nothing hangs and both USB devices (mouse and printer) work fine. FWIW, I first saw this the next time I booted up after a power failure; I don't remember anything in particular that I had installed, updated, etc. before then.
So far, since everything seems OK, I'm basically ignoring it except to think to myself, "Yep -- still there..." when I see it. If anyone thinks it's something serious, or if anyone knows how to get rid of it, I'd like to hear about it.