While I wasn't there to see it for myself, I don't think Strafe and theep would make up something like that for no reason, and considering who they are, I'm inclined to trust them on their word. Changing the IP: sure, sounds great. Another possible solution could be to bump up all MotK members one rank- one above the default but one below moderator, a new usergroup you could make with Permissions or GroupManager or whatever plugin you're using for that- and disallow building permissions for default ranked players.
That way, if someone joins the server, they won't immediately be able to rip and tear into things. Also, griefers people like adrian246 and fig_man_57 would go through a short phase of, "Yes, we know you're online and want to be promoted from Default to Member, but we'd like to get to know you first" to help separate potential griefers from people who wish to be a part of the community. I've suggested this for two servers in the past, one on which I was a mod, one on which I was an admin, and on both, there were fantastic results.
Edit: As for griefing to report, someone made the mistake of stealing all four beds from the community house. Obviously, as one person pointed out, the only reason someone would need to steal all four would be "so that other people can't use them." I've since replaced the beds, and would like for you to see who destroyed then stole them before I replaced them, DDR. Oh, and what was previously a small wheat farm within about ten blocks of the community house has had a large portion of glass destroyed- might wanna check that out, too.
How convenient, Adrian typing "GTG" and logging out IMMEDIATELY the moment I ask why he's bragging about having finished making TNT out of about 100 bits of gunpowder.