Problem and Solution; Critical Error: SiteUrls.Config ;
Unable to generate a temporary class...

I tried setting up Community Server several times in multiple ways, and kept
running into the "Critical Error: SiteUrls.Config" problem. In the
description of the error, the page would say "Unable to generate a
temporary class..."   I kept searching in these forums on "Critical
Error: SiteUrls.Config", trying the solutions (e.g., deleting temp files),
and still no luck.

 It wasn't till I searched on "Unable to generate a temporary class"
that I got a hint: security settings on C:\windows\temp.

 Make sure that your web site has access to C:\windows\temp by changing the
security on said directory.

I suspect this is the reason that so many people (as evidenced by the forums)
are having difficulties.