PyCharm does not highlight errors

I have a problem with PyCharm v2.7. it does not show me errors. I have configured it to show them as here but nothing. here a screenshot of what I see (no error displayed) enter image description here

if I run code analysis it shows the errors marked as INVALID in the window but it does not highlight the code. any idea?

Solution

I found. i've enabled by chance the "power safe mode" that avoid error checking. it can be re-enabled by clicking on the little man on bottom right corner.