If I clear the APC cache, the problem goes away. However, if I reload the page after it's cached, I get the error above. For now, I have disabled APC cache on the site and the page works. I added some debug output to the controller, and the "saveBillingAction" method is not called when the page is cached.
Any help or ideas?
We are experiencing the exact same issue. It's extremely unfortunate. We've had to keep APC disabled.
Our current strategy has been to combat APC being disabled with additional web servers, however, it's not economical long term.
We are looking into additional PHP Caching.
To the Magento team, this is a serious concern and your team needs to investigate it.
would the problem I'm having be the same as the checkout isn't working at all i press add to cart and nothing goes in the cart