It was
brought to my attention that my trac sites were no longer authenticating the generic user I set up. Apparently, something I missed in my switch to SCGI...
But it's not scgi-wsgi's fault, really.

I narrowed it down to mod_proxy_scgi (obviously, by the title of this entry!). mod_scgi works fine. mod_proxy_scgi does not seem to pass the HTTP Authorization header along. I'm currently looking around for flags/options to remedy this with no luck. A quick Google search
revealed something similar, but not quite. Though that may address the SCRIPT_NAME/PATH_INFO issues I've seen... in a future version of Apache HTTPD.
I wish I had more time to figure out what was really going on. In the mean time, I will probably switch away from mod_proxy_scgi (to mod_scgi) where possible...