You wipe cache and dalvik cache in red clockworkmod recovery. Go into recovery by either holding down the power button and choosing recovery from that menu, or by holding down the volume down, volume up, and power buttons until you see samsung flash for the second time, then let go of all three buttons. You should be in stock blue recovery, hit the volume down button once to highlight apply sdcard:update.zip and hit the home soft key. This will take you to red cwm, scroll with volume button to wipe cache partition but now in red you use the power button instead of the home soft key. When that is done scroll to advanced, hit the power button, scroll to wipe dalvik cache and hit the power button. When that is done, hit the menu soft key so you are back at the main red cwm menu again where reboot system now will be highlighted at the top of the menu, hit the power button and wait for the phone to reboot.