a) Go to Peopletools > Portal > Structure and Content. (Navigate to your component)
b) Go to security tab
c) Change the security to public(makes all permission list to go) and now again Permission List access (making all permission list to reappear).
d) Save the page
e) Check if the Permission list is shown after the save..
f) Now sign-out and delete the application server and browser cache.
g) Try login again and access the page