In 2002, Vishal had adapted a novel called
Pas de Quatre by Australian writer I.A.R. Wylie into a screenplay called
Timbuktu (or
Timbuctoo according to
Stephen Alter's book). His choice for the leads were Vivek (now Viveik, if you will) and Aishwarya Rai with Pankaj Kapur in a "key role." Vishal acquired the filming rights, Abbas Tyrewala worked on the screenplay; Pankaj Kapoor reportedly noted some discrepancies; Robin Bhatt was roped in for a rewrite, but things failed to proceed beyond this.
Kyun!... Ho Gaya Na killed the love for the real-life love birds at the box office, Vishal moved on to make
The Blue Umbrella, Vivek Oberoi returned to strum Wonder in
Omkara and Ms. Rai became a Bachchan.
Now, about 7 years later (aka saat saal baad), Rai-Bachchan and Vishal seem all set to team up on what appears to be the same project. Mrs. Rai-Bachchan notes that they had wanted to work with each other "ever since he was the music composer on a project that got shelved." One wonders if this was Hum Panchi Ek Daal Ke starring Sunil Shetty and Ashutosh Rana (in which Vishal reportedly gave KK his first solo song).
There's more about what happened all those years ago here.