The dispatcher doesn't seem to like map:redirect-to's as in:
<map:match pattern="gallery/**/index.xml">
<map:redirect-to uri="gallery/{1}/index_1.xml"/>
</map:match>
This is fixed in the photogallery by changing it to:
<map:match pattern="gallery/**/index.xml">
<map:generate src="
cocoon://gallery/{1}/index_1.xml"/>
<map:serialize type="xml" />
</map:match>
I'm really not sure what the benefit of the map:redirect-to is in this instance. It seems like the cocoon protocol might be more appropriate anyway but it highlights that there may be an issue with using redirect-to's in Dispatcher. Further testing is required to make sure it's really an issue, but it's not my major concern at the moment and I didn't want to get sidetracked.