Single Super-Admin Can't Edit Own (Old) Entries But Can Create and Edit New Ones

Old installation : Freelancer v2.0.0pb01 / Build: 20091211 [tried to upgrade and failed - long story]

Single user (super admin). I can’t edit existing channel entries created by myself. I can, however, create new ones and edit these. The indicator, apart from not changing is that on ‘submit’ of edited entry it directs me to default site page rather than the live-look page within CP with link to edit page. I’ve tried stopping and starting the system - logging in and out doesn’t help because this is tied to the ‘new’ me.

It feels as though EE believes there’s a an older instance of myself still live but not logged out. It’s set to use cookies + session IDs.

I haven’t found any way to stop this behaviour and allow editing.

Is there something I can nuke in a table in the underlying database that might help?