Yesterday I helped I friend who upgraded to WordPress 3.0 from WordPress 2.9.2. Many admin panel (post edit, plugin list and other) stop to show. Ususally it’s a memory problem. WordPress sets memory limit to 32 megabyte but if you have many plugins installed you can experience out of memory (and if you don’t have the error log to track the problem you only see random blank pages).
To increase the WordPress memory limit, you have simply to edit the wp-config.php file adding this line just below the “define(‘WPLANG’, ”);”:
that definition rises the memory limit to 64 megabytes. Do not set this limit too high: a “run away” of corrupted scripts can eat up all the server memory (if the server is your you freeze it, if you are hosted your account may be bocked).
To be more conservative you can set the new limit to “40M”.