right, i unplugged network cable, restarted and problem persisted.
i unplugged HDD, booted up, restarted, problem persisted.
put HDD back in, followed sicilian suggestion then restarted with and without network cable and still box wont restart until i physically switch off and on with power button at the back.
please note i had to perform the power off and on action immediately after reflashing with build 632 as it wouldnt restart naturally.
any other suggestions please?