After updating from v2.5.5 to v2.7.3, I get the following error:
A PHP Error was encountered Severity: Notice Message: Undefined property: EE::$session Filename: controllers/ee.php Line Number: 41 Fatal error: Call to a member function userdata() on a non-object in /......../admin/expressionengine/controllers/ee.php on line 41
I feel like I have done this upgrade loads of times and I cannot work out where I'm going wrong here. I have overwritten all files as usual. The CP works fine.