Portia de Rossi rehab treatment is allegedly caused by a spat in her marriage with Ellen Degeneres; the month-long program last May was kept under wraps.

In Touch magazine reported marriage trouble as the reason for de Rossi's time at rehab, which peaked into an argument about their $40-million estate in Holmsby Hills. Reports from numerous sources claim de Rossi checked into Malibu's Passages, a clinic known for treating substance abuse problems (smh.com.au).

The In Touch report maintains Degeneres supports the treatment, visiting de Rossi regularly on the weekends throughout her stay. Neither have confirmed or denied the validity of the report, though.

Source to the magazine hinted at the argument which allegedly contributed to the rehab: "Portia hadn't been happy for a while and was drinking and isolating (herself), and Ellen confronted her. Portia lost it and blamed Ellen for driving her to drink because of her controlling ways and said she wasn't in love with her anymore. Ellen was crushed and screamed at Portia to get out."

Clues to the Portia de Rossi rehab treatment are evident in their personalities, according to the source.

"Ellen is domineering and Portia is passive. Ellen always calls the shots, and Portia never complains. She felt like a prisoner in her own home. She went from sipping white wine occasionally to drinking at least a bottle or more a day and topping it off with a pill. It got to the point where she was out of it four nights a week. They've had vicious shouting matches -- with both of them yelling cruel, soul-crushing put-downs that they both deeply regretted."

If the reports of the spat and the rehab are confirmed, the couple is putting up a brave front in the media, especially for Degeneres. They've reportedly gone through couple's therapy and considered divorce, but are still willing to work things out even after the alleged Portia de Rossi rehab stint (mercurynews.com).