Paul Greengrass, who directed two of the Jason Bourne films — including the most recent offering, The Bourne Ultimatum — has walked away from the Bourne 4 project. Matt Damon might not sign on too.

Details are still sketchy, but it would appear that Greengrass wasn’t happy when Universal brought in up-and-coming writer Josh Zetumer to work on a ‘parallel’ screenplay for the film, rewriting the one already penned by Ocean’s 12’s George Nolfi.

Greengrass has already been under pressure from Universal over the way he’s handled the budget on the forthcoming Green Zone, which has suffered reshoots and a $150 million pricetag.

If Greengrass has left Bourne 4 for good, Damon could well decide to remain loyal to him and refuse to shoot with anyone else.