Earlier quoted context omitted.
Maybe it's changed, but walking a customer through clearing some specific cookies was a common help desk thing. To deal with shitty websites...PayPal had this problem for a long time where you would get an obscure error until you manually cleared a cookie. This will be harder, especially where you need to clear cookies on different domains like a login page, saml page, account page, etc.
You had to clear one cookie on Paypal and leave the rest? Jesus Christ, what a nightmare! Do you happen to recall what situation that was? Just curious to read in a Daily WTF sense, not challenging you to prove it.
If I remember right, clearing it for one site didn't help because clearing "login.paypal.com" cookies didn't clear "some-other-thing.paypal.com" or "www.paypal.com". They seem to use www.paypal.com for everything now.
Google for: "paypal Your browser sent a request that this server could not understand" for one example
Or "paypal your last action could not be completed" for another.