PE is calculated based on expected future earnings. Different analysts have different expectations of growth and timelines, hence the inconsistent PEs. If you want to know the "real" PE look at the current share price and the past year of earnings and figure it out that way.
yahoo and others use TTM for eps, others use expected. In acquisition laden stocks you shouldn't really pay attention to p/e though. Lots of merger costs drive down earnings, even though cash flows can be robust.