O.K. i have Rooted the phone (SuperOneClick) and managed to install xrecovery, I had to pull the battery to re-boot, went into xrecovery...wiped the cache and did a full factory restore (full wipe), rebooted the phone...worked for a while then froze again
I waited for a couple of hours and tried the phone again and it worked (for a while)...
It seems to me that the touch screen is the thing that is freezing it...If i leave the phone alone for a couple of hours then i can unlock it, but if i try to change any settings ( say sounds/display/wifi) it will freeze again.
Cheers