Screenshot of problem: http://www.equinefocus.co.uk/worderror.jpg

I create a table without problem, but when I come to type in it, the cell fills with a navy highlight, and I am unable to see the text I am writing, until clicking outside of the cell. I do not have this problem at work, so I wondered if I've clicked an option somewhere to cause this.

Any help correcting this issue would be greatly appreciated!