By accident I disabled the 'Media' module in my orchard installation yesterday.
It turns out that this completely breaks Orchard. Neither frontend or backend works afterwards, and even the command line module dies.
This makes it a bit hard to re-enable the media module.
I finally managed to fix it by editing the database, but I took quite a while to find what to change.
It might be an idea not to allow uninstallation of basic modules? Or at least to provide a 'failsafe mode' where modules can be re-enabled?
Just an idea...