use filebox (install it if you dont have it) then go to....

usr/share/applications/hildon-status-menu

inside the folder you will see all status menu in your phone....look at the end of all files there must be .desktop at the end...if you have other names after .desktop then delete the name & after the .desktop....
now you have mention you did install powatool right??? if you do then at the same folder there will be one folder called...

usr/share/applications/hildon-status-menu/disabled

look at that folder & see if you have disable the volume control...if you do then use powatool to enable it again then reboot....