[Plugin: Google XML Sitemaps] build: WRITING error message

The error message I get for the site build of my blog on the SOE plugin for my blog:

‘There was a problem writing your sitemap file. Make sure the file exists and is writable.
There was a problem writing your zipped sitemap file. Make sure the file exists and is writable’

I am not a programmer – what do I do?

http://wordpress.org/extend/plugins/google-sitemap-generator/