# Typing Control-6 makes text cell disappear

This morning, I opened a document I worked on last week, and all the lines of text that had Control-9 functions in them where the function involved a power written by typing Control-6 were completely mangled. They were either just huge cells of white space, or huge mainly white cells with the odd symbol thrown in with line-breaks in the middle of partially-displayed functions. The document was fine when I closed it yesterday.

Today, even a completely new document displays the same problem. I start a new text cell, type (say) "Text ", then Control-9 to switch to input mode, type s[x], hit Control-6 to raise s to a power... And the text cell suddenly exhibits the behaviour described above. The document is instantly unusable.

In the pictures below, all I did was type Control-6 at the end of the function:

What's going on, and how do I fix it?

UPDATE:

1. MacOS, fully up to date.

2. Quitting and restarting Mathematica doesn't solve it. Neither does restarting the computer.

3. Changing text colour (sometimes) amplifies the problem - adding acres of blank space and making text that was visible disappear.