Cloudmark false positives causing rejection of incoming mail

[#1]

Anyone else getting problems with this? (That you know of, that is.)
Mail to my personal domain gets redirected to my Plusnet account. This morning, Plusnet started rejecting the redirected emails, because, as the rejection message puts it...
host mx.avas??.plus.net [??.??.??.??]: 550 IP ??.??.??.?? is DNSBL listed. Please see http://csi.cloudmark.com/reset-request/ if you feel this is in error.
Note that it talks specifically about DNSBL listing, not the famous Cloudmark reputation index. So I looked at some DNSBL checkers - nothing at all. My domain isn't blacklisted anywhere I could find. I tried the Cloudmark reset request, but that just told me that a reset request had already been submitted for that IP address.
Now, I might think this was just a one-off, but two days ago Plusnet started rejecting all emails from a friend of mine with the same error. Again, his domain wasn't blacklisted anywhere.
Has Cloudmark gone a bit haywire?

[#2]

Responding to this as I have exactly the same problem. follow the link in the message to reset the reputation but nothing changes.

Did anyone find a resolution to this false positive? 

[#3]

Send me a direct message with details/IP etc. and I'll try and pick it up later this week.