Yes, you have a problem of permissions in your server. You can manually install aulawiki, if you have ftp access...
Download it from http://www.escire.org/aulawiki/mods (under features, aulawki 0.5 is in there, newer even if the number is lower, than 1.2 available through http://tikiwiki.org/mods
(I wish, for next times, the author - jyeres - didn't find problems in cvs at sf.net to keep using the central cvs for upgrades..., instead of his own one, as nowadays).
Unpack it in local, see the structure of directories, and browse your tiki installation to find the place where it should be installed (I don't remember right now). If you search it but you can't find it, ask again.
Btw, so far aulawiki development and bug reporting is being done aside tw.o sites. See it in : http://www.escire.org/aulawiki/