Am currently running a similar hardware setup but not on a Dell machine. One thing to look at would be the driver settings from the Nvidia control panel. When you open it (right click option on empty display space for me) there should be a task pane on the left side (Display/Adjust desktop color settings/2.Choose how color is set.) Make sure that 'Other applications control colour settings' is selected.
The other item to point out is that many graphic intense software packages (Adobe products, SolidWorks, amongst others) and some games as well also have provisions in them for taking over control of the monitor(s) settings and colour profiles when they are running. Many of these also run accelerators at startup which sometimes change settings you don't want them to. It may be necessary for you to change their preferences or options so that they will use the calibrated profile as well.

Hope it is something simple,
Jeff