I updated the otherwise-excellent BarcodeScanner App on my LG Optimus phone and it stopped working. After the update the program just gave me a black screen with a red line on it. A quick search of an Android forum proved I’m not the only one who had this problem, it happens on all Optimus models.
The fix is simple. Uninstall the app and install the old version which can be downloaded from http://code.google.com/p/zxing/downloads/detail?name=BarcodeScanner3.72.apk. Done.