I have ATI Mobility Radeon HD 5470 on my HP laptop. A few weeks ago I was confused with a weird trouble in proprietary drivers for my graphics card. When I start X server (or just boot Windows) system sometimes totally hangs up with black screen. The most annoying thing is that issue appearing is absolutely random (2 success, 3 fails, 1 success, 7 fails, etc.). It appears both on Linux (Arch, Debian 7) and Windows XP. I've tried reinstalling OS, drivers, etc. I've also tried updating BIOS. Then boot was successful for the next few times and issue appeared again (probably it was just a coincidence, because another BIOS updates gave no results). I really don't know what to do. Any ideas?
Well, the workaround I've found for that issue was to hibernate laptop instead of shutting down. After few months laptop stopped booting at all (black screen after pressing button and nothing else). Then I've figured out, that my AMD chipset is dead. I replaced it, and it helped.