In our company I had really bad experience with enforced speed settings on Cisco switches. No matter what was set on client side, behavior was hard to predict, includind unexpected link losses etc. Especially with devices such as Brocade's Fibre Channel Enterprise Directors (devices that I manage) or EMC Clariion disk arrays.
Out network team was insisting on enforced speed settings (for reasons unknown to me) on Cisco side but once they swithed the setting to Auto everything went back to normal.
Thus my advice would be to at least giving a try to Auto option on Cisco side. If linkspeed needs to be enforced, try enforcing on client side only.
Never mind I found the link to the linknegproc.exe util in the other thread http://communities.intel.com/thread/23859?start=15&tstart=0
This util solves the problem for us as well.
But I'm confused as to why the the network controller still does auto negotiation when the driver is set to forced. I mean why present the user with the option to change speed and duplex settings if it's just getting ignored anyway.
Maybe this should be fixed in the next driver release.