Connection between DisplayLink and TV keeps dropping

[MacPhyle]

Well, I'm not sure which connection it is, but my Macbook thinks the image is still displaying on my TV. (The window displayed on the TV doesn't move back to my Macbook.)

The cable doesn't seem that long; it's 6 feet.

This was all working much better (infrequent occurrences) until a couple of months ago, then this problem started getting worse. As for what I was doing a couple of months ago, I had to my Macbook back to Apple because of a problem with the battery. It may have been before I'd sent it back or after it returned, but sometime recently I reinstalled the Displaylink software driver. It seems like it has something to do with my Macbook's display going to sleep. I mean, that seems to be when it happens. But I've always let my display sleep and it worked fine before....

Any further ideas? Thanks for your help!