i had come across this yesterday, and i think this is what you're referring to.
don't know how credible the site is though, but i'll post it anyway.
Nvidia blames amd for dropping physx support - The Inquirer
"So imagine the embarrassment for Nvidia when a few weeks ago the firm, with all its "quality assurance" practices, uploaded a beta version of its Forceware drivers that supported the very thing that it said adds to its cost and brings down the quality of Nvidia's products. Like cross-vendor Physx support, Nvidia dropped the driver quickly, though not fast enough because punters and review sites managed to grab copies to see what the current state of play was with AMD's well received Radeon 5870 and 5970 cards.
When the lads at Tweaktown went to, er, town with a couple of AMD's finest, the results were not all that surprising. As AMD's Radeon HD 5970 is pretty much the fastest GPU money can buy and doesn't require you to live next door to Sellafield, the writing was on the wall for Nvidia."
so it looks like they were just beta drivers, but have since been pulled.