I am starting to think that this film contains two stories. The stories are basically the same story being told in a different way.

To get a glimpse of this idea in the making, please visit the thread "Diane's BS at the party (Split)".

The first story is being told with a 60's style framework. The second story is being told in a modern style framework. (There may even be a third story here, I'm not sure yet.) The story ends when the box is opened. The box opening also restarts the story and is supposed to happen each time the story is told. I'm not sure if the retelling of the story is linear (meaning time passes each time it's told - and it's being told in a different way each time) or if there are only two (or three) versions that continue to play over and over simultaneously.

Something has happened, an accident, causing parts of the retro story to appear in the modern story. And vice versa.

Examples:

*Rita belongs in the modern story
*Betty belongs in the retro story
*Dan belongs in the modern story
*Diane's apartment belongs in the retro story
*Aunt Ruth's apartment belongs in the modern story
*Winkies belongs in the modern story
*Pinks belongs in the retro story
*Adam belongs in the retro story
*Bob Brooker belongs in the modern story
*Laura Harring's car crash belongs in the modern story
*Blonde Camilla belongs in the retro story
*Coco belongs in the retro story
*Cowboy belongs in the retro story
*Joe belongs in the modern story
*Diane (while in the modern story) is a misplaced Betty, and that's why she's missing
*Mr Roque belongs in the retro story
*Blue-haired Lady belongs in the modern story

From the IMDb forum:

Could the story being taking place in multiple eras???

I think that it's very possible if the stories are running linear. Every time the story starts again, time has passed. And the story changes a little to suit the times.

Aunt Ruth´s apartment looks distinctly retro

Aunt Ruth's apartment could have been built during one era and still be around in another, later, era. It would still have obvious features, now matter how it is decorated, from that previous era in which it was built.

Ever bought a house that was built in the 50's? :)

Diane's apartment, however, is still decked out in the retro era. Old appliances, including that fan on her mantle.

and she herself, for all intents and purposes, belongs in a bygone era

Aunt Ruth looks very modern to me when we see her at Havenhurst. She looks very retro when we see her at Sierra Bonita. Her looks change (along with her age) yet again when we see her at the airport. She may be the common thread between all of the stories and belongs in each and every one of them.

Sights of her may actually be the clue as to how many story variants are being intermingled.

Dan may give us the clue as to who is intermingling them. The bum.