sleeps mode seems to break delay()

Hi Daniel,
Referring to an earlier post regarding permanently battery powered devices, I'm trying to implement a system in which most of the time the MCU sits in the panstamp.sleep() mode. But as soon as the sleep mode exits through an ISR, the ISR function works correctly but when it reaches a delay() function, it just hangs there. I've tried putting a panstamp.wakeUp() function at the start of the ISR function but with no success. Is it possible that the sleep mode interacts with the WDT timer which sleep depends on? Some solution around this would be appreciated.