^If it were his screen:
2) A screenshot wouldn't capture it
3) Rebooting the OS wouldn't temporarily fix it, since a screen isn't software
4) We wouldn't be able to see it (see reason #2)
I left out step one just because starting lists with the number 1 is played out.
That doesn't mean I know what it is, but it's definitely something graphics/software related... a restore should fix it if some files got corrupted or altered.....