1- revert to your stock rom.
2 - wipe/factory reset in samsung stock recovery
now your phone is completely clean
3- flash TWRP on this thread with Odin
4- then factory reset and wipe cache on TWRP
5-flash CM10 and gapps
Hey, I just flashed the Dream Kernel and softkeys came back. Thanks for your reply though....
Anyway, before I flashed this ROM, I was on the update dated 17/9/12. My phone kept rebooting randomly.
I installed the 21/9/12 and then I was getting screen flicker & the phone keeps rebooting randomly. I'll probably go back to an ICS rom now, just until the JB one becomes more stable.