Translating the term Billing ïn the core file (version 1.7 of civicrm-core.po) gives an error in the contribution pages: when go live or testing there is the error: "Please set a location of Billing.
When I put the original term: "Billing" back or leave it untranslatted than the error is gone. It looks like the contribution feature is depending on the term 'Billing' not on the variabele.
Re Piotr Szotkowski::
It seems we indeed do some string matches and not consider translations there. Please file an issue in our issue tracker for this bug.