Dennis Quaid's wife has filed for separation.

The 'G.I. Joe: The Rise of Cobra ' actor's spouse, Kimberly Buffington-Quaid, has announced the split just six months after she originally called off a divorce.

A representative said: ''Kimberly and Dennis Quaid have decided to legally separate after eight years of marriage.

''They ask that their privacy and the privacy of their family be respected during this difficult time.''

Kimberley, 40, is requesting joint legal and sole physical custody of the couple's four-year-old twins, Thomas and Zoe.

In her original divorce papers - filed in March after eight year of marriage - Kimberley said things between them had ''become insupportable because of discord or conflict of personalities.''

However, in April she cancelled the proceedings, saying they were going to give their marriage another try.

A source connected with the couple told website TMZ the reason for the renewed split is that ''Kimberly is fed up with Dennis' cheating and wants out of the marriage. He's not a good husband.''

The couple recently moved to California, where there is a six month residency requirement before anyone can file for divorce, meaning she will have to wait a few months before she can proceed further with the separation.

Dennis, 58, and Kimberley have already overcome a great deal, as their twins almost died shortly after birth because they were accidentally given a massive overdose of a drug at hospital.