I have a similar problem with an Asus U30Sd notebook, Windows 7 and Nvidia 520M graphics card
A couple of weeks ago I noticed laggy screen performance and low FPS. I do not know exactly when the Nvidia card stopped working.
(1) Windows Device Manager>Display adpators does not detect the Nvidia card. Only detects Intel HD 3000. There are no Device Manager errors or strange devices
(2) Nvidia driver v267.21 does not detect card
What I have tried:
(1) Checked Asus website for driver updates. Found I already had the latest recommended BIOS (v213) and Nvidia driver (V220.127.116.1121 - ie Nvidia v267.21). This was because I had a similar problem about a year ago. That time I fixed the problem by upgrading to the Nvidia v267.21 driver. I do not remember if I could see the Nvidia card in the device manager before I fixed the problem.
(2) Uninstall Graphics drivers, download and intall latest Nvidia driver from the Nvidia website v320.49 (recent stable release 1 July 2013). This did not detect the card.
(3) Full system scans with AVAST and Malware Bytes-found nothing
I do not know if the card is fried or if it is a software issue. Given that I had a similar issue caused by software a year ago I suspect software. I do not know where to go from here.
A friend of mine had the same problem Have you tried forcing an unexpected reboot , You see the drive hooks a function by patching the system core table so it's not safe to unload it unless another thread is about to jump in there and do its stuff. And you don't want to end up in the middle of invalid memory. Lol