Thankyou very much! It's working again - it was the script file. I had wondered at something earlier this evening but had forgotten to mention it (it was after my second post). Two scripts I had tested when I was looking to see what was happening, hadn't worked right. Then when typing a normal word, it activated the script for something that used a different word...
It was a particular script, and I had only added one new one to the file in the last couple of days. I just removed that script and everything is now working fine.
Also thanks to Drake for the links.