The former couple - who announced last month they have called time on their 10-year marriage - reportedly clashed over their conflicting attitudes towards fame.
A source said: ''It was a struggle for Chris to have this movie-star lifestyle. He hated the paparazzi attention. They started to realise they didn't have as much in common as they would have liked.''
Another source added: ''Gwyneth is someone who likes attention. There is a narcissism there.''
It is also believed the former lovers - who have children Apple, nine, and Moses, seven, together - struggled to cope with their diverging personalities.
An insider said: ''[Gwyneth] is earthy and open-minded. I would describe her as a sort of pampered bohemian.''
Another friend added to People magazine: ''She's funnier than people realise. She's not prissy - if anything she can be pretty crass. [But] you get the sense her crowd is a very jet-set, money crowd, and it's not necessarily his crowd.''
Meanwhile, the Gwyneth, 41, and Chris, 37, are determined to stay friends for the benefit of their children.