ok… there was an error being reported in my 404 logs on my site, even though all files were in place and permissions correctly set.
The error was being caused at my server level with a bad directive in .htaccess.
Once corrected, things worked smoothly.
This in mind, there are several things that can create, edit, alter and interfere with .htaccess and redirection within wordpress, including wordpress permalinks, any plugin that creates permalinks, alters, redirects or intercepts them (such as SPF and hundreds of other plugins).
.htaccess can also discriminate according to browser type, agent, referer, ip and host name.
Given the number of errors being reported with issues, and the seemingly indiscriminant way the errors are effecting different browsers, servers, and installs. it may be time to take a closer look at prety permalink codes, and the effects of choosing different permalink structures, page deapths, and custom page placements.
