We have CustomPress installed on a variety of sites and it seems to be constantly throwing alerts in the log files stating 'PHP Notice: Trying to get property of non-object'. I could not tell where this issue was coming from at first since it is listing lines 4564 4566 & 4568 of the /wp-includes/query.php file. However, when I went through and disabled all of the plugins, the notices stopped when CustomPress was disabled. Once I figured that out, I noticed that the same issue is occurring on all sites that have CustomPress installed. Can you check the plugin to see what might be causing this issue?