Shipping / Billing address problem
This bug one only seems to be affecting existing stores, see tlnlounge.mycafecommerce.com/ for an example.
When a user specifies that their billing and shipping address are not the same, and they press continue, their shipping address is changed to match their billing information. If the user clicks "Modify information", they can see that their info has been changed to match.
I tried to reproduce this bug a test store, but new stores seem to use a different checkout sequence.