This is usually caused by accidentally setting the cursor color to be the same as the paper color. It may also be a consequence of an video display driver and display hardware incompatibility - see technical bulletin 1022.
To check the cursor color, and change it if needed, click and display the Set Up menu:
Click on Colors; you'll get the "Select paper color" dialog. The current paper color is displayed in the New Color box (here it's #7) and it is outlined in white on the color chart. Since color #7 is white, the outline only appears to make the white color patch look a little larger in this case.
Assuming that you wish the paper to remain white, just click the "OK" button. You'll now get the "Select cursor color" dialog - be careful! It looks just like the paper color dialog, but it controls the cursor color, not the paper color. The current paper color is displayed in the New Color box (here it's #0 - black) and it is outlined in white on the color chart.
With these settings - a black cursor on white paper - the cursor should be visible.
To change either the paper or the cursor color, simply click on the color patch of the desired new color. To leave the color as it is, just click OK without making any color patch selection. You can make as many selections as you like - no change takes place until you click OK. When you have selected the color you wish to use, click OK.
Be careful - the sequence of events is fixed as:
