I believe that I have read the existing posts to no avail regarding the UltraSharp u3011 monitor sleep mode problem.
My setup includes two external monitors: (1) a display port USB 3.0 connection to a StarTech DisplayLink plug and play module driving a Dell UltraSharp U3011 monitor, and (2) an older Dell 24" monitor (driven by a DisplayLink plugable USB 2.0 Display Adapter) these external monitors are attached to an ASUS N53SV-XR1 laptop (with 16GB RAM running Windows 7 Ultimate). This setup has worked for more than three years with no problems. The older 24" Dell monitor does not go into sleep mode. The U3011 is also connected to a Panasonic Blueray disk player using the HDM1 connector and there is no sleep mode problem when using the Blueray player. (I manually switch the U3011 between DisplayPort and HDMI modes.)
Any help or insights would be most welcomed.