Under 3.1.2, when installing the plugin, I get a "The plugin does not have a valid header." error.
This is what I get when automatically installing the plugin:
Downloading install package from http://downloads.wordpress.org/plugin/wp-readme-parser.1.1.zip… Unpacking the package… Installing the plugin… Destination folder already exists. /home/gwyneth/gwynethllewelyn.net/wp-content/plugins/wp-readme-parser/ Plugin install failed.
Strange, isn't it?
None of the suggestions/comments here apply to it: http://wordpress.org/support/topic/wordpress-28-the-plugin-does-not-have-a-valid-header?replies=24
And clicking on the (inactive) plugin to activate it afterwards certainly worked for me, so I wonder if this was just a temporary glitch when unpacking it (after all, the ZIP file is created by WordPress.org) or some weirdness...