At random times local sites don't allow me to login to admin with certain browsers. Currently I cannot login to a site using Chrome, but can using Firefox. I have had sites that won't login with Firefox, but do with Chrome.
The error is a browser console error, not a Craft/Twig error:
Failed to load resource: the server responded with a status of 400 (Bad Request)
I've renamed and deleted cpresources (as another post had mentioned to try), but this didn't work.
It happens at random points too. I can login fine then come away from my PC for a few minutes to return to a login screen and not able to login.