Hi there. Running a Radeon HD 7970 with the latest drivers, and found that OpenGL has ceased to work entirely. I've tested multiple applications, including CAPS viewer. DX11 seems fine.
Using Windows 7 Ultimate x64, 16gb of Ram and an Intel i7-2600.
Fixed it myself; looks like there was a compatiblity issue with Stardock Windowblinds, an application for reskinning windows. Uninstalling Stardock fixed the issue.