Shipping costs (unknown amount added)

[shiver]

All seems to be working ok now after carrying out your advice, any ideas what the problem was?

[Toby B]

It looks like the problem is a small bug. The records in the OrderTracking table are not purged when orders are purged. This can cause a problem as some orders might look at old records which causes the shipping calculation to be recalculated and increases after downloaded.