Mysqld + php-cgi cpu usage

[mjnet]

Hey guys

I'm configuring a new webserver on amazon ec2 with ubuntu 11.1.
everything works fine, just the ultra high cpu usage of mysqld and php-cgi.
a larger query or a couple of smaller queries at once will push cpu usage to 99%.

i've heard this problem could be due mysql locks?

i just wanted to ask if anybody of you already had the same problem?

thanks a lot!