"It's a pretty terrible thing to find out in any way. Sandra learned about this from a tabloid hours before the tabloid took the story public," People's senior editor, Kate Coyne, told "Good Morning America." "To be ambushed in that way, she was completely stunned."
The star couple looked happy at the Oscars in early March, but Bullock failed to mention James in her acceptance speech for best actress, fueling media speculation that she may have known about his infidelity then. It turns out that like her adoring public, she was blissfully unaware until the tabloid magazine In Touch published the bombshell report less than two weeks ago, according to People.
"Everyone we spoke to ... made it very clear Sandra had no idea it was going on," Coyne said, citing "very close lifelong friends" of Bullock. People's report hits newstands later this week.
People also reported that Bullock and James were not seeking divorce attorneys, contrary to online reports.
James reportedly had an affair with Michelle "Bombshell" McGee, a San Diego tattoo and fetish model who, according to reports, also worked as a stripper. McGee claims to have more than a year's worth of text messages relating to the affair.
Bullock's co-star on "The Blind Side," Quinton Aaron, told People Bullock was "picture-perfect" during filming.
"I learned so much from working with her. I don't think she was aware of any alleged marital problems and always spoke highly of her relationship with Jesse," Aaron said. "My heart goes out to her in this trying time, and I know she will overcome."
Though Hollywood often seems like the center of the universe for infidelity allegations, the same drama plays out on a less public scale in homes across the country. But experts say there are ways to sniff out infidelity and, if it's found, how to deal with it most effectively.
According to therapist Bethany Marshall, there can be several clues when one partner may be having an affair.
Pervasive pattern of selfishness. Does he or she only worry about self-gratification?
Excessive secretiveness. Does he or she erase texts from his phone? Screen calls?
Sudden interest in his or her appearance. Is he or she suddenly working out and losing weight?
Renewed interest in sex or trying different sexual practices.
Isabel Gillies, an actress and author of a book on infidelity called "Happens Every Day," said that she had no idea when she was being cheated on.
"People are surprised that you don't know," Gillies said. "But I see a lot of people in these book groups and say 'Does anybody think that their husbands would cheat on them?' and everybody answers 'no.' It's just sad, and it's important to look at both sides of the coin and try to see the other person as a whole."
If there is infidelity, Marshall said the next step is to determine what kind of problem the relationship is in.
"There's three types," she said. "There's the one-time colossal mistake with an otherwise good guy. There's a guy who cannot handle the marital stress. And then there's the guy who always wants narcissistic gratification."
Marriages can survive infidelity, Marshall said, but a few things have to happen first.
Offending party has to be sorry. "He [or she] has to be willing to repair the damage by showing remorse," Marshall said.
Admit the affair and why it happened. "If you can't articulate it, how can you fix it?" she said.
The offender must make a plan to fix the problem.
Gillies said repairing the relationship requires both parties, however.
"It's a complex situation," she said. "I think it's important also when somebody does something that's socially unacceptable like an affair. The person who has had the affair happen to them can sort of put a halo on and say, 'You did something really bad.' It's important for both partners to look at how they work together.
"One person can't be a devil and the other can't be an angel," she said.