Inconsistent incoming trackbacks

I have a similar problem.

For example, kevinkane.com/2010/12/4-studies-which-show-that-using-a-second-monitor-can-boost-productivity/ doesn’t show the trackback from http://gkrb.com/blog/No+Brainer:+Add+a+Second+Monitor+to+your+PC

My settings allow pingbacks and trackbacks.

Can anyone help? Thank you.