A bit of a blast from the past, but I just had exactly the same problem and discussed possible causes with Corion on the CB:
[kcott] I got this message in CB: "root says root just sends automa
+ted notices, but you tried to reply "" to it." ...
[kcott] It's been noted before: Strange message in chatterbox ...
[kcott] I was working in Nodes to consider at the time (if that mat
[kcott] I assume I've just clicked the wrong button or link. Does a
+nyone have any ideas what might have caused this? I'd like to avoid a
[Corion] Maybe you tried to /msg root with one or more spaces afte
+r root, or something like that?
[Corion] Yep. Whenever you /msg root the check doesn't even look at
+ whether you're actually trying to say something :)
[Corion] /msg root
[Corion] Hmmm. I must be misreading the code in message because my
+attempts at saying nothing elicit no reply...
[Corion] Ah - code comprehension error. You need to have a message
+from root, and you need to reply to it. Then, even if you say nothing
+, you'll get that message.
[Corion] At least that's my current reading of message. Later I mig
+ht get a different reading, in a more sonore voice.
[kcott] Thanks for the follow-up Corion. I just tried to look at my
+ nodes Nodes You Wrote and got: "kcott has no writeups, it seems.Serv
+er Error (Error ID 8658203b6489)". Possibly not something I did?
[kcott]: We got a little out-of-sync there (my last response followed
+your "Hmmm... " line. I did have a message from 'root' (about a reply
+ to a node) which I deleted - probably just miskeyed/clicked somethin
+g ... phone call ...