Answered my own issue, and posting my outcome for anyone else with the same issue.
I started out by un-installing, and re-installing the plugin, and then going to http://<my domain>/sitemap.xml
I noticed the timestamp was stale, so I manually deleted the file. Then I made another mistake - I thought that updating the settings for XMl-Sitemap in wordpress would automatically re-generate the sitemap.xml file - it didn't. In addition to that, I got a few errors because I had deleted the sitemap.xml previously.
I then noticed a "rebuild sitemap" manually in the Xml-Sitemap page, from within my WordPress installation, clicked that, and Viola! I was in business and all my pages were there.
Ultimately, I think what got me, was that making changes to the settings page for this plugin, didn't automatically re-generate a new sitemap.xml - which was just a silly misunderstanding on my part.
Thanks for the plugin!