I am not able to replicate your problem. I took a sample photo from Windows, pasted it into Word copied it, pasted it into Paint, made some changes, saved it as a jpeg. Back to Word, imported it, copied it, pasted it into Paint and was able to draw on it again.

Is this what you're doing?

Yes, that's just what I did. In the end I decided to start all over again and created what I need. One small point though. I found Paint to be a trifle cumbersome. Is there anything more effective I could try to do the following?
The idea is to create a membership card for an Angling club.
1. Scan a section of a map.
2. Insert a Text block holding a series of venues each one numbered.
3. Insert a number on the map scan next to each venue.

Paint has come a ways, but remains a relatively primitive application. What you're trying to do is quite elementary. I would suggest that you either invest in simple photo-editing program or download a free one. The are a number available on CNET and other sites. you might also consider whatever version of PhotoPlus is being offered for free by Serif, which offers older versions for free. I have used a number of Serif products and have found them quite adept.

Many thanks. I will have a look at PhotoPlus.