[Plugin: All in One SEO Pack] Fatal Error with WordPress 3.0

Your memory limit is quite low at 16M and it looks like your hitting that.

WordPress tries to raise the limit to 32M but I guess your host is blocking that – so you need to talk to your host about raising the memory limit for php.

In 2.9.2 you were lucky to run with a 16M limit – we already had code to raise the limit to 32M if the host allowed because 16M is not really enough especially once you install a few plugins.

In all likelihood you were just able to run with 16M previously and now with the extra features in 3.0 you are going over that limit.