Excessive CPU problem in FC5t3

[bloch at verdurin.com]

This evening I put FC5t3 on a Vaio S1XP, previously running FC4.

The desktop is almost unusable because of severe system load spikes,
meaning that windows are unresponsive for ~10 seconds at a time.

Text consoles don't seem to be affected, so I don't think it's a kernel
issue.

Happy to report a bug, but I'm not sure what the component would be?