I have found that windows can stop later drivers from installing some parts of the driver. go to c drive then open the AMD folder, open the folder of your latest driver.
open CNext or CNext64 folders depending on weather your computer is 32bit or 64 bit
then click on ccc-next in the CNext folder OR ccc-next64 in the CNext64 folder
it will install the driver, no need to reboot
Not sure if this will help you but give it a try, helped me with missing dlls from the drivers
These latest drivers don't like other monitoring/tweaking software and these can break the driver and alter its settings