Have Dual monitor setup with host ATI Radeon HD 4600 as primapr and USB 2.0 UGA as secondary.
Host is Windows 7 64-bit. USB 2.0 UGA driver is V5.6 from Windows update.
When returning from sleep both screens are black. Mouse cursor is visibleand can move across both displays. BUT noting I can do changes displays from black. until I remove the USB video adapter. Then the primary comes back to life.
After bringing the primary back to life Ican re-plug the USB 2.0 UGA and the secondary returns to operation.