7.3 inline editing bug

I have just finished upgrading to 7.3 from 7.2 and have an inline editing bug. When I try clicking to edit a record I get the following error (img attached). Anyone else run into this?

Did you run a Quick Repair & Rebuild in Admin -> Repair and ensure permissions were set correctly post-upgrade?

Thanks,

Will.

Yes, I did the quick repair and rebuild and I even set all permissions to 777 for all folders and files, still same error.