Mid 2011 27" Imac with Amd Radeon HD 6770 M V Ram 512 MB, Model A1312
This has been a completely reliable machine for seven years. The only repair has been a hard drive replacement 2 years ago.
Now appears to be infiltrated by a ghost just in time for Halloween.
First Spotify started playing a Beegees song unprompted.
Then pages loading in browser start building from the bottom of the screen in horizontal lines that scroll up and repeat themselves over and over without stopping.
Scrolling with mouse not working.
Multiple screens keep building and overlapping.
Restart fixes the problem for a few hours; then symptoms return.
A candidate for a video card bake?
Or some other problem?
Many thanks for any advice.