Re: Upgraded to WPMU 3.0 now BORKED
log into your hosting backend (file manager) program – ie the files of your WP install and rename the “plugins” folder to something else – maybe “plugins-hold”.
This will disable all plugins. You should then be able to log in to WP and activate plugins gradually to find the evil one.
Battled the White Screen of Death a few times – take a deep breath, it’ll be OK, even though it gets your pulse racing!