This problem should have been resolved by our update to SL4.8.
Occasionally the gam_server (the Gnome File Alteration Monitor) process enters a loop and starts eating CPU.
In general, it is safe to just kill gam_server. It will then be started automatically when needed. Adding the following to ~/.gaminrc may help prevent it from looping and using up CPU (once gam_server has been restarted).