I have the same issues of intermittent sudden connection dropouts as reported by others with the Intel Centrino Advanced-N 6235 Wifi adapter and the Intel Proset 15.x drivers!
My system is a brandnew desktop computer with an Intel i7 3770 Quad-Core CPU, an Intel Z77 chipset, an Asrock Z77E-ITX mainboard, 16 GB of RAM, and Windows 7 64-bit.
Previously, I already encountered the issue with this adapter's predecessor, the Intel Centrino 6230 and only managed to resolve it by going back to an older driver version. If my memory is correct, the Intel Proset 14.x version range worked flawlessly, but the 15.x drivers lead to the dropouts (I always use 64-bit drivers).
These can occur randomly after 5 or after 50 minutes. The adapter suddenly disconnects and won't reconnect to the wireless network unless it is reset. The wireless router itself is fine as there are over a dozen devices from all types of brands that connect regularly to it without any problem at all.
The fact that the problem occurs on two different cards (6230 and 6235) leads me to believe that there is a driver problem.
On the 6235, going back to a 14.x driver does not seem to be an option on the table, because the device seems to be only supported by 15.x versions. I already tried going back from the recent 15.2 version to the previous 15.1.1 (after uninstalling through the device manager), but the problem still persists. Now I just went back to 15.1.0 and it's been ok so far, but i'm not very optimistic.
I have tried different changes in the driver settings but with no success. The problem persists!
I'd be thankful for a solution.
Edited 9/5/2014 by John S. (Intel Customer Support).
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The 17.1.0 version of Intel® PROSet/Wireless Software and Drivers has fixes for connectivity related issues with the Intel® Centrino® Advanced-N 6235 wireless adapter. If you are still experiencing connectivity issues after installing the very latest software and drivers and you require further troubleshooting, please contact Intel Customer Support. If you prefer to ask questions, make comments, and/or receive answers on this support forum (Wireless Networking Support Community), please start a new thread or find an existing thread that matches your specific issue with your specific hardware/software.