This post was dated back Oct 9, 2008 at EC2 Ubuntu thread.
Unfortunately, after several months of the running instance as a test machine, and when php5-dev package is installed, the error comes up. CPU spin lock!
Solution #3 is applied to the running instance, snapshot EBS and spin up the latest AMI ami-1c5db975 from www.alestic.com.
Change the Elastic IP to the new running instance with the new EBS snapshot attached and viola… its ready to go!