The downloads plugin 1.1 from geeklog.fr happens to use a gltext class, which does perfectly co-exist in geeklog 2.0.
Somehow geeklog 2.1 now loads by default a different gltext class, so the downloads plugin breaks with error "cannot declare GLText twice". Besides the plugin/gltext.class is quite different from system/classes/gltext.class.
Usage in geeklog2.1 is in lib-common in COM_renderWikiText and COM_checkHTML
So, what to obsolete now? lib-common or the downloads plugin?
What *standard* is followed now?
Dengen introduced the new gltext class to Geeklog 2.1.0. It now handles the rendering of the articles and comments.
Dengen is also the author of the Downloads plugin. I believe he is working on an update (hopefully he will see this post and add his comment) which will I assume use the newer Geeklog gltext class.
As a work around you could rename all instances of the gltext class in the downloads plugin to something else.
I will send him a quick email and get him to respond.
One of the Geeklog Core Developers.