Three ways I use to get out of CLOCK LOOP:
Insert a damaged Audio CD.
Plug in the network cable and wait for 15 minutes,
watching the system reboot like crazy. --- You can
also try with no network cable, and wait for 15
minutes again.
Rapidly press the A button or START button during
boot-up and thru the reboot.
Worse case of CLOCK LOOP I ever had was 2 hours
of rebooting.
Are you sure it is CLOCK LOOP?
Signs of CLOCK LOOP is normal bootup complete
with the big X with MS logo, and then blank
screen with a little blob or just part of green orb
before it reboots to the big X with the MS logo.