Chrome Compatibility Problem?

I was working on making the ScopeRoller website a bit smarter, especially to simplify keeping everything up to date when shipping costs change.  While trying to get my clever Javascript running, I discovered that I could no longer add orders to the PayPal shopping cart:

HTTP Status 405 - Request method 'POST' not supported

It turns out that it wasn't my changes.  The existing code that my customers use worldwide with Internet Explorer and Firefox does not work with Chrome.  I wonder how many other browsers have the same problem.  One more struggle to go through tomorrow.

UPDATE: Apparently something that required deleting PayPal cookies to fix -- and a pretty recent problem, according to some accounts.