I tried all 5 steps you recommended and nothing worked. I had to reinstall wp.
The funny thing is that I have 2 different wp blogs in the same domain and server and when I reinstalled one, the other one started working too.
Today, I was on the admin pages of one of my blogs and I got the following error:
Warning: gzuncompress() [function.gzuncompress]: data error in /[my full path]/wp-includes/http.php on line 1792
After that, both blogs failed to load the css in the admin / dashboard pages.
Any help?