Mysterious Pingbacks on a Single Post

We are receiving mysterious pingbacks on one particular post on a WP 3.1 site. They all contain text similar to “[…]while the sites we link to below are completely unrelated to ours, we think they are worth a read, so have a look[…]…”

Every time I check the linking site in question I find no such text in any of their source code and no links to our WP site, direct to the post in question or otherwise.

I have not had to request much help with WP before now so apologies in advance if I am posting this in the wrong area or if I have somehow missed information about this type of issue. So far google searches have failed me.

We have received almost 30 of these spam pingbacks in 8 days, and I am concerned that someone may be artificially boosting our page rank via temporary off site linking or something to that effect. Maybe I’m just paranoid but this is a critical support site I’m running and this is the only unexplainable traffic to it I have ever seen.

Thanks in advance for any advice/tips/etc