I ran into a problem this plugin was causing with one called Post Types Order. The developer of that plugin spent some time looking into it and determined the cause. Here's what they had to say:
We checked into this and the issue appear to be an unexpected query return, which expected to be as string but returned as array instead. Per WordPress codex this behavior is expected when multiple post types are queried but not one. The issue was produced by Display Posts Shortcode but we updated our code to handle such situations. I've uploaded the last files to your server, everything appear to work fine now.
Just thought you might like to know.
http://wordpress.org/extend/plugins/display-posts-shortcode/
