Until calibre or stanza straighten out the urlencode issues, here's my simple script to fix the urls on the stanza.xml file:
http://pastebin.com/m1dc17a20
to run, do:
# python thiscode.py path/to/stanza.xml
This just replaces the spaces and commas with url-encodes equivalents (but not the parenthesis, since stanza apparently doesn't like that)