I fixed this problem by removing ProSet and going back to the base driver for the 82579LM that is supplied by Microsoft with Windows 8 (version 12.0.150.0 - 29/02/2012). The problem did not occur once in the last month of heavy use.
However, yesterday I upgraded to Windows 8.1 RTM. Looks like the newer version of the Proset driver has been supplied to Microsoft (12.6.47.1 - 28/03/2013) for Windows 8.1 and now the problem has resurfaced for me. I don't know what it is exactly, but there has been some regression in the driver code from 12.0.150.0 (29/02/2012) to 12.6.45.0 (and above) that is causing this issue.
I hope this can be identified and sorted. Thanks.
