In a written statement, the company said:
"Sky HD is launching on time today but we are having to change some installation dates because of delays to HD box deliveries. We ordered more than enough boxes to meet demand and we're ready to install them but they're not arriving from our supplier as fast as we agreed.
"We think the fairest approach is to keep installations in the original order. Although this means that any delay to the first installations may have a knock-on effect on others, we believe it is important that those who requested Sky HD first will still be amongst the first to receive it.
"We're very sorry for any disappointment this has caused and we're working hard to resolve the situation. Thousands of customers will have their HD box this week and many more will be installed in time for the start of the World Cup. We'll do everything we can to bring HD to everyone as soon as possible."
Discussion about all aspects of Sky's new high definition TV service are taking place around the clock on our dedicated Sky HD forum.