USB Display Adapter - worked, now dead
 

I added a USB Display Adapter to my Win 7 PC a few weeks ago, and it was working great, connected to a flat-panel TV as a second, extended monitor. Earlier this week I had a major crash in my windows system, related to an application using a Dynex USB card reader. On the restart after the crash, the main monitor was stuck in 800x600 mode, and it took me several reboots and messing with the display settings to get that straightened out. Now, I cannot get the second monitor to work on the USB Adapter. I have removed the software and driver (including using the Display Link removal program) and installed the latest downloaded software several times. The install and start-up seems to go normally. The USB Adapter device shows up in my Windows device list. The display control shows no second monitor. I forced it to look at "VGA" but still no display. Most of the time the second monitor (TV) shows "No Input", but it has also shown "Mode not supported". Nothing has changed in my hardware setup. Any ideas?????