Notebook Asus K53xx
I have had the same problem. i5-2410M running constantly and exact 0,76 GHz. Several reboots didn´t nothing. Booted with with Hirens (WinPe based toolbox) got the same result - constant 0,76GHz. After a normal Systemboot and the problem was solved. I don´t now what is happend. The Hirens didn´t change anything on my system.