This is more of a comment than a problem (since the actions below solved it - read on for more info).
I was getting random vertical black lines in excel spreadsheets. I have three monitors. Two are controlled by a R7 370 Series and the main display is controlled by a R9 290X.
Both the 290 and the 370 had drivers dated 08/22/2017.
I did an "Update Driver" searching automatically for drivers on each device. The 370 retained it's 08/22/2017 driver but the 290 found a "new" driver dated 6/27/2017.
After I did this, the problem with the black lines went away.
Not sure why this worked but it did fix the problem. Thought I would add it to the knowledge base. This was very frustrating for the few weeks that I had the problem. Note, that it only occurred with Excel. No other programs, downloads, browser or other errors were observed.