Back in 2010, there were some rumors that Zooey Deschanel would play Ada Lovelace in a movie called "The Enchantress of Numbers." Apparently she actually wasn't going to play her, but what ever happened to the movie? Did it ever exist in the first place?
It seems like this was one of those movies that just vanished. Any googling immediate turns up a plethora of pages mostly within the same week period, all with the same details, and nothing else.
The movie was going to star Zooey Deschanel as Ada Lovelace. It was going to be directed by Bruce Beresford. (see here or here). It was also going to star Billy Crudup as her husband, William King, and Toby Jones as Charles Babbage (see here).
The most information I can find, from the final link above, is:
Beresford plans to shoot the period drama, which would chronicle the time they spent working together, in the autumn [of 2010].
However, as you comment, Zooey pulled out of the project. There doesn't seem to be any information after that. I can only speculate that the film simply fell through (possibly due to not finding a good lead, or a dislike of the script) and all parties moved on to other things.