make sure session is not deleted?

[habreu]

I have a bothersome issue that happens once in a while. Some customers don't get charged shipping (we are using some custom upcharges coded by Miva). I have been unable to reproduce this - if I enter all the same information and address etc I do get charged. The only thing I do not is that if you delete the session string

i.e. shopping-cart.html?Session_ID=0123464b90bafce00d168f280b761 3

during the checkout process you don't get charged shipping. I'm not sure if this is something fixable, and if so if it is simple enough for me to add or I need Miva.

Your thoughts?

[AHerb]

You can switch to full SSL (https) and get rid of sessions completely.
I believe Miva is using sessions to transfer the data between HTTP and HTTPS