Reset CPU speed at boot up

Asus P4s800 m/board 2000Cell cpu. I have noticed over the last year that occasionally at boot up I am told that the cpu speed has been changed and to reset this in Bios and restart computer. This has happened since new, seems to happen after downloading/installing/uninstalling something, causing an error then next reboot have to do this with the cpu. Is this a fault with the Bios, all other Bios settings do not change and are up to date, so can not be battery. Or is this a fault with motherboard/CPU. I have just ordered another M/Board to see what happens. I sell a lot of these m/boards and alway use Cell cpu’s, first time this has happened. Any ideas Thank you