Fatal Error–tried all solutions found

I was getting the error a lot, and I tried every solution I found, including getting the limit increased to 64M by my host. None of that worked. Then I trimmed down my plug-ins and fixed a few things and it went away. But now I’m getting it again–every time I try to update to 3.0.1. I’m down to eight plugins and I want all of them. I also want to update WordPress.

This is the error:

Fatal error: Allowed memory size of 33554432 bytes exhausted (tried to allocate 2966269 bytes) in /****/******/public_html/sargemarcori/wordpress/wp-includes/class-http.php on line 1408

I have tried adding ini_set('memory_limit','64M'); to install.php. I have added define('WP_MEMORY_LIMIT', '64M'); to wp-config. I added the suggested line (forgive me, I deleted it so I don’t have it handy) to my .htaccess file and it made my blog unable to find my admin page. I went into wp-settings to change the limit, and there is no memory limit that I can see. It reads` // Set initial default constants including WP_MEMORY_LIMIT, WP_DEBUG, WP_CONTENT_DIR and WP_CACHE.
wp_initial_constants( );`

I have searched and searched, but while lots of people have had the same problem, one of the above solutions seems to have worked for everyone else.

I have checked–the host did, in fact, inrease the limit in the php.ini file. Any suggestions? I am no code-expert, so please bear that in mind and give me step-by-step help if you can.