Comment notification, but no comment!

As of a few hours ago, I’m getting (hundreds) of email notifications that there’s a comment waiting to be approved, deleted or marked as spam. But when I click the ‘mark as spam’ link, WordPress takes me to a page that says “Oops, no comment with this ID.”

Now some of the notifications are for comments that have already been approved, that were made months ago.

I use the Akismet plugin, slightly modified to go through a proxy which my host insisted on.

Is this a weird type of spam, or a glitch in the notifications? Is there anything I can do about it?