Thanks Gustaf. We updated xowiki today and my first test was not successiful, but I will try again during daylight hours.
Here is what I added to the folder object:
#######
# this is the payload of the folder object
set subst_blank_in_name 1
set index_page "en:DOM"
#######
I will double check if we got the change and report if it is not a local issue.
Here are some relevant links from the Wikipedia for reference:
http://en.wikipedia.org/wiki/Wikipedia:Naming_conventions_(technical_restrictions)#Plus
http://en.wikipedia.org/wiki/Help:Page_name#Ignored_spaces.2Funderscores
http://en.wikipedia.org/wiki/Wikipedia:Canonicalization
