More info...
After playing around a bit I narrowed down the issue by editing things on the syntax page until I localized the source of the problem to this line.
{{rss>
http://slashdot.org/index.rss 5 author date 1h }}
So it seems it has something to do with pulling and embedding the rss feed.
I did a little research and found that docuwiki seems to use simplepie for parsing. So I downloaded simplepie and ran the compatibility test and that seems to indicate everything should work OK.
Is there something else that I should be looking at to sort this out. For now I will leave the code block example and just remove this embed line and at least that will allow me to look up syntax as needed, but I'd like to sort out the problem if possible.