Macbook pro stuck on loading screen

Hi

I have a Macbook pro 15" mid 2009 unibody.

After the recent update sometime last end of the year my macbook stuck on the loading screen. I left it like that and waited until it went all the way to finish. But to my surprise it didn't get to the login screen and keep on showing loading screen with the loading bar.

I have searched for the fix and tried everything, like:

reboot / disk clean / all the other hack / you name it.

Finally when I reinstalled the OS it fixed the issue and the loading screen took normal time and I get through the login. Everything seems to be working fine. I finished my work and close the lid and when opened it again it was frozen. I force shut it down and I am back to square one.

Same loading screen issue, stuck again.

Any Idea what could be doing that? hardware or software? any fix?