CMS Made Simple Forums

i have a problem . i am working on a project which uses smarty . the problem is that, when i make some changes  on the contents of the file on the admin side which in turn saves it successfully in the database but the files  under /tmp/templates_c / is not  getting updated . i cannot save it  manually either  . i tried changing its permissions but it does not change .it resets the permissions to its original form . plez help me