Although I had the inclination to fix this limitation in my upgrade code, truth of the matter is that we don't really support installing onto paths with spaces at all that well in the first place. I tried configuring MacPorts sources to install onto "/opt/mac ports" to test a fix and I couldn't even get past that very first stage. Now I know the OP had MacPorts in the default /opt/local, but the path leading up to his home dir (where MacPorts also looks for files) did have spaces in it ("/Volumes/Litter Box/Users/(...)", if I'm not mistaken).
MacPorts put aside, Unix software in general behaves very poorly with paths that contain with spaces, needing escaping and/or quoting all around to bypass them. So, in general, I'd really recommend against this setup.
Thanks for the report, though, will turn it into a FAQ entry for later reference! Closing ticket.
-jmpp
