Nope, this isn't going anywhere anytime soon. And it's none of these - although the tweet about elevator music does come close.
The most popular rumour doing the rounds is that Jay Z has repeatedly renaged on a promise to help his sister-in-law's career.
A source told the MailOnline: 'Solange is so angry because Jay Z promised to give her more help with her career and when she brought it up again the night of the gala, he told her he just didn't have the time to work with her in the studio. He hasn't kept his promise to help her. Jay keeps telling her to give him some time and he will sit down and write with her and then get her into the studio but he hasn't done it yet."
Prior to the drama, Beyoncé and her sister were seen dancing up a storm on the dance floor with Naomi Campbell, (that could explain a lot...) while the Jay, 44 "hung back at one of the fireplace areas."
Another report circulating is that Solange is annoyed (presumably on the behalf of her sister, who probably couldn't give two hoots) that Jay Z "made plans to attend Rihanna's Met Gala after-party without Beyonce." This comes courtesy of the NYDailyNews.com.
The most viable rumour, however, is that Solange was making a show of herself and Jay Z told her to keep a lid on it. She had previously been clocked roaring at designer Rachel Roy, before informing several arbitrary females to stay away from her brother-in-law.
A source told Us Magazine: 'Solange was yelling that anyone who gets close to Jay has to be warned and deal with her as a sister.' A second insider said: 'Jay said something small to her along the lines of, 'You are out of line.' Solange was being a loudmouth and snapped at Jay trying to calm her down and get her out of there.'
Apparently this is no biggie 'cause Solange has been known to lose the rag, so Bey and Jay are used to it... All I know is, if I attacked one of my brother-in-law's in a lift in front of one of my sisters, I'd be sent packing.
While we're at it, people reporting on this need to learn how to say Solange. It's So-lawnge, not "So-laaahn-gay" or "So-lang-gee" as she's repeatedly being referred to on Ireland AM. Yes, I watch a lot of Ireland AM.
In other news - Jay Z brought Solange jewellery shopping yesterday, for realz.