I found a strange behaviour on the RW 6.3.8 (15165) blog page and the theme Wilderness 5.1
When I select a post or a category, the navigation menu disappears and you cannot go to other pages.
I’ve replied to your email, in response to receiving a link to your test site and a copy of the RapidWeaver project file.
I can confirm that this appears to be a bug in RapidWeaver, not specifically the theme. It seems that in any RapidWeaver theme where the RWAlwaysDisplayFullNavigation key in Theme.plist is set to NO (to generate a block or split navigation layout), RapidWeaver is failing to generate page navigation links on the individual blog entry pages.
Another confusing factor is that you had some bad Google Analytics code in the page too, which was causing a breakage. A script that had been linked to for tracking visitors was missing, and the resulting Javascript error meant that not all the code for the navigation menu was being run.
I could replicate the same problem of missing page links in several themes, including Aqualicious, Birthday and Business. The suggested fix is to contact Realmac Software and await them to diagnose and fix the problem in the next update. In the meantime, it might be wise to revert back to an older version of RapidWeaver for the time being.