Its connected to the configuration of your Server.
From memory and to fill in others your server is running with open_base_dir in operation and will require modifications to the TIki source code. or the server config changing.
I wouldnt use 1.9 for any production site we have some big parse_data bugs that prevent wiki pages from being rendered. tikiwiki.org is not currently using 1.9 lastest CVS. but a checkout from about 12 August 2004.
If you have these problems:
cvs up -dP -D 12Aug2004 -r BRANCH-1-9
will get your site back to some kind of stabilty