The forums indicate that this problem is due to a windows update rendering a graphics driver non-functional (card in my case is Intel 4000). If first happened about a month ago, so I updated my graphics drivers and this resolved the problem for a while. It has now come back. Not sure why - no recent updates to my system. It occurs simultaneously with “É” being produced when I type “?”, but this is easily resolved by pressing control+shift twice. I have looked for several of the reported updates (eg KB…) that may have precipitated this on my system and have not found them. The last windows related update on my PC was 18 Oct 2017, and sketch up was working fine subsequent to that (after I updated the drivers), which are current at present.
The previous thread related to this seems to have died a few months ago, and I have tried all things on the tread, but still have the problem.
Any further advice would be appreciated.