I have Xsane on Ubuntu 12.04, with the scanner/printe/fax SAMSUNG_SCX_4729_FW. When trying to scan an image, with preview window open, and clicking the button "Acquire preview", I get an error message "failed to start scanner: Scanner cover is open". Of course, the cover is OK; I tried to switch my comp off, the printer off, etc., the same result. I also tried to scan without the use of preview window, but the problem persisted. A regular printing using the same Samsung machine still works perfectly. Any idea how to fix it?
It turned out that Scanner cover was indeed "open". Unfortunately, the error message was not too specific: the guilty party was one of two hinges at the back of the cover (to be precise, a lower side of the hinge that is supposed to plunge into the body of the scanner) -- the one which was near the left side of the scanner. That part was not fully inserted -- just slightly off... Once I applied some force to it, it went down to a complete stop, and the status light changed from red to green. To bring the scanner to its normal operation mode, I had to turn it off and then turn it back on.