Simsalabim Solutions

Sometimes you simply don't get the correct name of an user permission you want to check with user_access().

So maybe just try this with Devel Module and Execute PHP Code:

dpm(user_roles());
dpm(user_role_permissions(user_roles()));

Tadaaa!

Edit: Just realised an alternative way without Devel and PHP is Fast Permissions Administration Module. I think since 7.x-2.5 you can display machine readable names under people -> permissions unsing "Show system names". So keep your modules up to date ;)