I’ve exactly the same problem on my site, since I’ve installed WordPress 2.3. I ve got IIS on MS Windows 2003 Server, php 5.2. I tried each solution in this post and no one fixed my pb ..
I’m looking for a solution for months, I ‘ve lost more than a half of visitors because of this pb : 40% of hits present the message “CGI Error…”
I was a fan of WordPress, but since this pb, that nobody can solve, I’m very disappointed.
I hope someone will find the pb.