Try resetting your Resharper options back to their defaults.
Resharper -> Manage Options -> Reset all settings
If that fixes the problem then I guess you've turned something off along the way.
Question
I have two solutions within VS2012, one a branch of the other.
I have installed the latest version of resharper (8.0.2).
I open the same .cs file from both solutions.
On the one I get the warning triangle saying that I have unused directives, (which I do). On the other I get no warnings or errors. I have also noticed that the cleanup code feature within the one solution is disabled.
How can I enable this feature?
Solution
Try resetting your Resharper options back to their defaults.
Resharper -> Manage Options -> Reset all settings
If that fixes the problem then I guess you've turned something off along the way.