What you people are seeing is what's known as a mismatched e-ticket. There are two parts to every booking, the PNR which is a record of the space held. Your e-ticket is essentially your authority to travel, when a BA ticket is changed with no additional collection or refund required then a revalidation of the eticket will match up the PNR nad the e-ticket. If a refund or additional payment is required (miles or money) then the booking has to be queued to the e-ticket department who will debit any additional money (Servicing debit miles if needed) and subsequently reissue the e-ticket to match the PNR.

The previous poster was correct in saying that the most common reason for OLCI not working is a mismatched e-ticket. Sometimes they match perfectly but a reavalidation is needed to push OLCI into working. With regards to the baggage allowance, your e-ticket has a record of the baggage that you are allowed. Sometimes this is recorded on e-tickets as incorrect but you won't have any problems with checking in the full allowanc that you're entitled to.