I just installed co-authors plus 2.5.3 and all seemed tickety boo. New edit box appears at the bottom and authors are auto-completed.
All looks good in the dashboard - i.e. dual authors appear, but in preview or publish mode, just the single author appears.
I am using a simple child derivation of Vigilance, with no custom post.php or page.php. I saw a reference to known issues with the thematic themes that pointed to co-authors not returning a value.
I also tried testing it on my local multi-site instal to ensure that it is not something in my child theme. Same issue applies with Vigilance itself.
Any ideas ?
Many thanks in advance.