AMD confirmed grey lines or screens with certain Radeon HD 5000 series GPUs is a known issue and that this bug will be fixed in an upcoming Catalyst driver hotfix.
Earlier this week, it emerged that many 5000 series users were experiencing problems with crashing and grey or colored lines appearing on his or her display. The grey screens and hangups were occurring while users were gaming, watching movies or in some cases, when the computer was just sitting idle.
When users contacted customer service they were told the issue was caused by a Windows 7 update. ATI recommended a clean install of the graphics card driver as a possible fix, stating this had solved some users problems.