LyX now won't display text on screen

[John O'Gorman]

Hi

Help!

After messing about with trying to insert 2 jpeg  images, I now cannot 
see any of the text.

It is still there and appears when I convert to PDF via pdflatex.

In LyX itself, where the text should be there are brownish thin lines.

I've looked at the lyx file itself (with vi) and cannot see anything wrong.

The same file copied to other Linux machines and an iMac all still 
behave OK under LyX.

My machine is an Acer Aspire V 15 Nitro running LyX 2.3.3 on OpenSUSE 
tumbleweed

We've already reinstalled LyX and LateX - no difference

I would be grateful for any suggestions?

Regards

John O'Gorman