At the moment I can only think of two things, either the step in the task sequence isn't referencing the Driver at all and so is not including your driver in the search or it isn't the correct driver file.
What happens when you manually install the driver using "update Drivers" on the display device in device manager to point directly at a folder with just the main driver files that you have imported into SCCM, does it install OK?
What method are you using to set drivers within the Task Sequence the default "Auto Apply Drivers" step or have you setup "Apply Driver Package" steps with WMI to select only certain models - Check the client logs too as one of them lists the device PNP ID search and should show you what it is doing on, ie whether its finding the driver and ignoring it or not.