http://www.dbform.com/html/tag/drm
http://wenku.baidu.com/link url=DykRyVGrvpLkfHUMrgoUOKghYXLAzh3YRSu1AHksMwdSmL5b8XtEcEocQcC 7ziRrzd6OF54w9w4TBHuHo486MsXwJFhBrtKe5r3jdtA8joS
http://www.laoxiong.net/problem-caused-by-drm.html