Wikipedia says:
"By the late 1960s, things were going wrong for Albert and Paola. Both were allegedly having affairs, and lived apart for a long while. There were even rumors of divorce plans. But by the early 1980s, things had improved well for Albert and Paola. It is said the Prince’s brother, King Baudouin, acted a mediator between the two. Even their daughter, Princess Astrid’s devout Roman Catholic faith might have played a role. In the end, Albert and Paola chose to stay together. For her 70th birthday interview, Paola, now Queen of the Belgians, said, “we’ve had our problems, but now we both say that we were meant for each other. We are very happy now.”"
from the royalforums
"However, soon after the marriage, the first cracks in the shiny surface appeared. Although the love between Albert and Paola was more than real for several years, they both suffered from the paparazzi, who had chased the glamorous Princess during the engagement, and who didn’t leave them alone during their honeymoon in Majorca. Princess Paola was often seen leaving stores through the back door, because the press would follow her everywhere. Paola was the Belgian style icon of the 1960s, but she herself would never admit to that. “I’m not a star” she would say in an interview, “I’m a woman like all other”. But between her and Queen Fabiola, she was definitely the more glamorous of the two.
Soon after the marriage, the couple was blessed with three children: Philippe (1960), Astrid (1962) and Laurent (1963). But the loneliness of the young princess weighed her down, and, to the utter annoyance of her sister-in-law Queen Fabiola, Princess Paola didn’t hide the fact that she sometimes considered her life as princess difficult and heavy. She was homesick and her leaving her beloved Italy was very difficult on her. Although the Princess enjoyed the glamorous part of her new life, she felt like the price she payed was sometimes too much. Especially her loneliness and the strict Belgian protocol were difficult to deal with. She became estranged her from her husband, who had his escape route with his motor bikes and his work. She didn’t find an ally in her sister-in-law either, who seemed to disapprove of almost everything the young Princess did. Later she would say that it was difficult to adapt to her new life. There was nobody to guide her, nobody to help her. “At that time, I really would have wanted Queen Astrid to be there”, she once said.
In the mid 1960′s, Prince Albert started leading most of the Belgian economic missions, and he traveled abroad a lot. Princess Paola at first accompanied her husband, so they both soon alienated their children. But after a while, Paola stopped accompanying her husband, reportedly because she was always so bored, and as a result they grew apart more and more. Their children suffered from the alienation between the parents, but Albert and Paola continued on their own course. While Paola spent a lot of time in Italy, Albert performed his duties, and both started having extra-marital relationships. While the couple did appear relatively happy in public – they posed as a happy family for their tenth wedding anniversary, at a time when Albert has already fathered a child with his mistress, Barones Sybille de Selys-Longchamps (which he never publicly admitted) – their love had withered and the divorce papers were ready to be signed.
But King Baudouin and Queen Fabiola strongly opposed a divorce, and so the couple remained together for many years, each living their own lives. By the time the King and Queen finally consented to a divorce, Albert and Paola had found each other again. How this miracle happened, nobody knows for sure. Was it Princess Astrid who brought her parents together again? Was it the Charismatic Movement? Or a couple’s therapy weekend? Fact is, that Albert and Paola really loved each other again by the time their daughter got married...ueen Paola gave the most candid insight in her relationship with her husband. “We had our difficulties”, she said, but “ora diciamo ch’eravamo fatto l’uno per l’altro” – now we say that we were made for each other.It is true that King Albert and Queen Paola have travelled a long way since they first met. Today, July 2, 2009, they celebrate their 50th wedding anniversary, and everyone who sees them together knows that they are a much loved and loving couple. They have succeeded in overcoming their difficulties and they love each other all the more for it."