Problem with upgrade to 3.0 and SEO software.

I upgraded my website to WordPress 3.0 on Friday night and reactivated the plugins one by one. When I reactivated All In One SEO, my website (both front and back end) became a white screen. I did the usual thing of renaming the file, and attempted to reactivate it again. Again I got the white screen. I have subsequently uninstalled the plugin and tried two different SEO plugins. Both of which have given me the white screen when I activate them. I find this infuriating and I’m at a loss as to why it’s happening. Does anyone have any ideas?