I have the suspicion that this issue is somehow connected to the black screen problem.
I have switchable graphics Intel HD Graphics 3000 + AMD Radeon HD 7400M as well. After upgrading to Windows 10, the screen was flickering or darkened occasionally, and a black screen appeared for a long time instead of booting animation. Following the recommendations in an other discussion, I removed the graphics drivers and allowed Windows to update the driver to AMD Catalyst v. 15.200. The black screen still appears at booting (not so long though, but still not showing the booting animation). The bigger problem is that the Catalyst Control Center sets the majority of applications to unlocked in power sawing mode. Especially those which would require more power.
I suppose that the black screen is caused by switching between the graphic systems. The update for the driver turns off AMD graphics for tough processes letting the integrated graphics to cope with them. Therefore our graphic card remained useless apparently. I hope that this problem will be solved soon. Otherwise I could not recommend anyone to buy an AMD product.