Again, the IT problems of the airlines are their problem, not yours. The contract you have entered into is defined by the terms & conditions of the ticket which are clear: no charge for change of date/time.

How the airline fixes it is their problem, but they cannot charge you.

By the way, has anyone else noticed how totally absent oneworld4u has been since we pointed out a few "issues" with their proposed online ticketing for this sort of stuff?

I believe that the moral of this story is to always have at least one open segment and force a paper ticket until the bugs are out of the e-ticketing system. Never use Release 1 of anything - always wait for Service Pack 1.