In case anyone else find this useful...
I was having lots of disconnect issues on Win8.1 x64. On Windows 7 it worked perfect. So, on Win8.1 I have downgraded the drivers to 14.0.1.2 using the Dell download file R292654 and everything is working perfectly.
Both the shipped Win8.1 drivers, and the Intel drivers for download, have disconnection problems. 14.0.1.2 is fine.
Jim