I get
Code:
Warning:  Unknown: open(/tmp/sess_5tvr8ro4t3tm7og0qaph7eagq6, O_RDWR) failed: Permission denied (13) in Unknown on line 0

Warning:  Unknown: Failed to write session data (files). Please  verify that the current setting of session.save_path is correct (/tmp)  in Unknown on line 0
on all the pages of my site.

I did nothing to invoke this, it just randomly appeared. Any ideas why?