In postinstall-1.4-en.txt, there's the following text:
If you wish to enable image uploads then you must manually edit the
LocalSettings.php file to uncomment the \$wgDisableUploads line.
With mediawiki 1.5.8, that's wrong. The line which is to be enabled is
# $wgEnableUploads = true;
So, it's no longer *DISABLE* but *ENABLE*.
I created the postinstall-1.5-en.txt, from now the mediawiki-1.5.x will use that, it would be nice if you could test it before I close the bug, it worked for me.
More than a month has past, simple bug , let's be done with this.
Stick it with a silver spoon.