Topic: Cancan adds "select where ... (1=0)" to all queries

I installed Cancan (just added 'gem cancan' to Gemfile and ran bundle install).
Then all my data vanished from the screens: "No entries found". 
If I uninstall cancan, I can see the data again.

With cancan installed, development.log has lines like this:
./log/development.log:  Node Load (0.3ms)  SELECT `nodes`.* FROM `nodes` WHERE (1=0) ORDER BY `nodes`.`node_name` ASC LIMIT 0, 15
./log/development.log:  CACHE (0.0ms)  SELECT `nodes`.* FROM `nodes` WHERE (1=0) ORDER BY `nodes`.`node_name` ASC LIMIT 0, 15

Anybody know where this "WHERE (1=0)" is coming from?