Revert to previous older driver Catalyst 14.4. I was using newest driver 15.7 and LR 6.1.1 kept crashing and could not disable GPU acceleration in Preferences. I have Windows 8.1 64 bit, Radeon R7 260X, and now everything appears to be working in LR 6.1.1 even with the GPU on.. Only in the Develop module is the GPU utilized, I believe.
Adobe and AMD are currently trying to resolve problems from the Adobe forum reads.
I did a Custom install of Catalyst 14.4 and disabled installation of Evolve Gaming App.
Hope this helps,