Someone mentioned a problem similar to yours. They had to go into Device Manager and grab the Hardware ID and "whitelist" it to the INF file so Nvidia would properly detect and install the latest driver. Sounds more like an Nvidia bug if anything.
Sony is also the biggest proprietary company i have ever seen. Not saying that they are crap but they have a reputation of being proprietary.
Nvidia usually excludes OEM versions of their graphics cards from their drivers. The release notes for 257.21 even suggest to, quote, "contact Sony for driver support for Sony VAIO notebooks". Some time ago they wouldn't directly support Dell and Lenovo laptops either.
Usually this is because the OEM doesn't want to have to support the latest drivers without testing them on their notebooks, so they encourage people to only use the drivers they supply. In some cases, though, the OEM might have customised the driver and/or hardware to include features that the vanilla nVidia drivers don't support. So just to be on the safe side you might want to have the latest driver from Sony at hand, so you can roll back to it in case the new one doesn't work.