Mine does this too. I wouldn't worry about it. Macs don't have a BIOS and have to emulate it as a result. The time gets messed up too which you might notice upon boot before the boot camp manager corrects it (or OSX corrects it when rebooting into it). My previous Mac had some question marks in the device manager for things like the motion sensor (for the hd I think in case it is dropped) and Apple said it was normal.
My guess is the BIOS emulation on occasion tricks Windows into thinking there has been a hardware change with the nvidia audio. It could very well also be related to graphics switching too, but also because of the BIOS emulation. Again, I would just ignore it. It's just a little box that pops up and it's harmless. I installed a newer nvidia driver too with an inf I modified myself but it was doing this before then so that's not the cause.
NVIDIA DRIVER FIX
I had this same problem with The Secret World. Fix it by reading this thread and following ErwinCouman's advice:
Do NOT download the nvidia beta 304.79 driver through the links he posted because they will lead to the international version and the four lines you need to add to the file won't work with that one. Download the one that ill_gb posted on page 2 of the thread for the English version:
Follow Erwincouman's directions in his second post in the thread by navigating to the DisplayDriver folder and copying and adding his lines to the nv_disp.inf (Set Up) file. Here is a link to an image of where he put the two lines:
NOTE: I noticed when I was adding his first line of code that he indicated 3 places where they should go: on the first line under each of the 3 Nvidia devices sections. I actually found 4 in my file and made sure the line was added to all 4 sections. I also added his second line exactly where he put it in the strings section, which is near the bottom of the file.