Last week we thought that it was pretty much a lock that Natalie Portman was going to star in the coveted lead role in Alfonso Cuarón’s upcoming sci-fi film, Gravity.

After Angelina Jolie left the project (in spite of the studio’s best attempts to keep her on-board), the go-ahead was given to Cuarón to send out an offer to Portman (she’s been impressing people with her performance in Black Swan) in an attempt to snag a half-way bankable leading lady (although Portman is definitely not as bankable as Jolie).

However, it was just an offer that was given to Portman, one which she didn’t immediately accept. Supposedly she was going to read the Gravity script and decide by the end of this week. Well apparently the studio won’t mind too much if she turns the project down, as their top choice is apparently not Portman but rather bankable A-lister Sandra Bullock.

Cinema Blend reports from their sources that Warner Bros. is worried about Gravity making its money back at the box office considering that it’s supposedly 60% CGI and is described a sort of “Cast Away in space.” Most of the movie falls firmly on the shoulders of the female lead so it’s no surprise the studio wants the most bankable name possible to draw in audiences who might not be that interested in it otherwise.

Portman still has the Gravity offer on the table but should she decide to pass on the project as Jolie did then Bullock will step in. Despite Bullock’s inexperience with this type of movie, she is considered the safer choice by the studio because she’s proven herself to be very bankable (she did The Proposal and The Blind Side last year which combined grossed over $600 million worldwide).

It sounds like WB and Cuarón are at odds with who they want to lead Gravity. With the type of director Cuarón is, I’m sure he’d rather accept a smaller budget if he could have a better suited (if lesser known) actress, rather  than conceding to the studio and grabbing the biggest name they can get.

Although I bet Bullock would be dropped like a hat if Jolie were to suddenly show interest again…

If things don’t get sorted out soon on the Gravity front then the project could face further delays, which could mean that they’d lose their supporting star, Robert Downey Jr.

Cinema Blend‘s sources also state that secret meetings are going on with other actors, just in case Downey isn’t available. Gravity was supposed to shoot before Sherlock Holmes 2 but since that starts before the end of the year, the plan now is to shoot Gravity during a break in the shooting of the Holmes sequel. If Gravity can’t make that “appointment” then the studio may be in danger of losing Downey Jr. altogether because he has the high-priority superhero project The Avengers coming up (which will be released in summer 2012).

A big fuss has been kicked up about Gravity thus far (brilliant director, fairly big budget of $80 million, big name actors interested, etc.) and yet those involved can’t seem to get this thing moving forward as it should. Hopefully Portman decides to take the job (I’d much prefer her in the role) but if not, at least the studio will be happy with Bullock pretty much guaranteeing more butts in the seats come release day.

I really want to see Gravity and the less hitches there are the better chance of it delivering on its huge potential.

Stay tuned to Screen Rant for more news on the film’s development.

Gravity is scheduled to hit theaters on December 1st, 2011.

Source: Cinema Blend