I have a Windows 8.1 64bit desktop with R7 260X graphics board in dual screen (extended) mode. For 2 or 3 years it has worked fine with two monitors. However, for the last few weeks, the 2nd monitor comes up with white screen almost all of the time. If I reboot 10 to 30 times it will come up normally. The next time I reboot it will be white screen again. How can I fix this????